Quick Recipe Version (TL;DR)
Quick Ingredients
- 3 lb plum (Roma) tomatoes, halved lengthwise
- 2 tbsp extra-virgin olive oil, plus more as needed
- Kosher salt and freshly ground black pepper
- 1 tbsp olive oil + 1 tbsp unsalted butter
- 2 large yellow onions, thinly sliced
- 4 garlic cloves, thinly sliced
- 1 tbsp tomato paste
- 3 cups low-sodium vegetable (or chicken) broth
- 1/2 cup heavy cream
- 1 cup loosely packed fresh basil leaves, torn
- 1 tsp balsamic vinegar + 1 tsp sugar (optional, for balance)
- Croutons: 4 cups 1/2-inch bread cubes (about 6 oz), 3 tbsp olive oil, 2 garlic cloves (grated), 1/4 tsp kosher salt
Do This
- 1. Heat oven to 425°F. Arrange tomatoes cut side up on a sheet pan, drizzle with 2 tbsp oil, season with 1 tsp salt and 1/2 tsp pepper; roast 30–35 minutes until edges char and juices concentrate.
- 2. Meanwhile, cook onions in 1 tbsp olive oil and 1 tbsp butter over medium-low, stirring, 25–30 minutes until deep golden; add garlic for 1 minute.
- 3. Stir in 1 tbsp tomato paste for 1 minute. Add roasted tomatoes and 3 cups broth; simmer 10 minutes (add 1 tsp sugar and a pinch red pepper flakes if using).
- 4. Blend soup until perfectly smooth (immersion blender or upright blender in batches). Return to pot.
- 5. Stir in 1/2 cup cream, 1 tsp balsamic, and torn basil. Season to taste with salt and pepper.
- 6. Reduce oven to 375°F. Toss bread cubes with 3 tbsp oil, grated garlic, and 1/4 tsp salt; bake 10–12 minutes, tossing once, until crisp and golden.
- 7. Ladle soup into warm bowls. Top with crunchy croutons, extra basil, and a swirl of cream or cracked pepper.
Why You’ll Love This Recipe
- Deep, concentrated tomato flavor from high-heat roasting.
- Luxuriously smooth texture balanced by fresh basil and crunchy garlic croutons.
- Weeknight-friendly technique with make-ahead options.
- Flexible: easily dairy-free, spicy, or richer to suit your taste.
Grocery List
- Produce: Plum (Roma) tomatoes, yellow onions, garlic, fresh basil
- Dairy: Heavy cream, unsalted butter
- Pantry: Baguette or crusty bread, olive oil, low-sodium vegetable broth, tomato paste, balsamic vinegar, sugar, kosher salt, black pepper, red pepper flakes (optional)
Full Ingredients
Roasted Tomatoes
- 3 lb plum (Roma) tomatoes, halved lengthwise
- 2 tbsp extra-virgin olive oil
- 1 tsp kosher salt
- 1/2 tsp freshly ground black pepper
Soup Base and Finish
- 1 tbsp olive oil
- 1 tbsp unsalted butter
- 2 large yellow onions (about 1 lb), thinly sliced
- 4 garlic cloves, thinly sliced
- 1 tbsp tomato paste
- 3 cups low-sodium vegetable (or chicken) broth
- 1/4 tsp red pepper flakes (optional)
- 1 tsp sugar (to balance acidity)
- 1 tsp balsamic vinegar
- 1/2 cup heavy cream
- 1 cup loosely packed fresh basil leaves, torn by hand
- Additional kosher salt and black pepper, to taste
Crunchy Garlic Croutons
- 4 cups 1/2- to 3/4-inch bread cubes (from about 1/2 large baguette; roughly 6 oz)
- 3 tbsp extra-virgin olive oil
- 2 garlic cloves, finely grated or pressed
- 1/4 tsp kosher salt
Step-by-Step Instructions
Step 1: Roast the tomatoes for concentrated flavor
Preheat the oven to 425°F. Place the halved plum tomatoes cut side up on a rimmed sheet pan. Drizzle with 2 tablespoons olive oil and season evenly with 1 teaspoon kosher salt and 1/2 teaspoon black pepper. Roast for 30–35 minutes until the edges are lightly charred and the centers look jammy with some caramelized spots. Set aside; scrape any pan juices into the tomatoes.
Step 2: Slowly caramelize the onions
While the tomatoes roast, heat 1 tablespoon olive oil and 1 tablespoon butter in a large pot or Dutch oven over medium-low heat. Add the sliced onions and 1/2 teaspoon salt. Cook, stirring occasionally, 25–30 minutes until the onions turn deep golden brown and sweet. If fond builds on the bottom, add a tablespoon of water and scrape it up.
Step 3: Add garlic and tomato paste
Stir in the sliced garlic and cook for 1 minute until fragrant. Add the tomato paste and cook for another minute to caramelize it slightly—this boosts the soup’s savory depth.
Step 4: Simmer with roasted tomatoes and broth
Add the roasted tomatoes along with their pan juices. Pour in the broth, plus red pepper flakes if using, and 1 teaspoon sugar. Bring to a gentle simmer over medium heat, then reduce to low and simmer for 10 minutes to marry the flavors.
Step 5: Blend until velvety smooth
Blend the soup using an immersion blender directly in the pot until completely smooth and silky. Alternatively, carefully transfer to a blender in batches, filling no more than halfway, venting the lid, and covering with a towel to prevent splatters. Return blended soup to the pot.
Step 6: Finish with cream and basil
Stir in the heavy cream and balsamic vinegar. Add the torn basil leaves and cook for 1–2 minutes—just enough to perfume the soup without dulling the fresh herbal flavor. Taste and season with additional salt and black pepper as needed.
Step 7: Bake the garlic croutons
Reduce the oven to 375°F. Toss the bread cubes with 3 tablespoons olive oil, the grated garlic, and 1/4 teaspoon salt. Spread on a sheet pan and bake 10–12 minutes, tossing once, until golden and crisp. Let cool slightly on the pan for maximum crunch.
Step 8: Serve
Ladle the hot soup into warm bowls. Add a handful of garlic croutons to each bowl. Garnish with a few extra torn basil leaves and, if you like, a light swirl of cream or a crack of black pepper.
Pro Tips
- Roast for flavor: High-heat roasting concentrates tomato sweetness and adds gentle char for complexity.
- Low and slow onions: Keep heat on the lower side and be patient; caramelized onions should be golden, not fried.
- Ultra-smooth finish: For restaurant-level silkiness, pass the blended soup through a fine-mesh sieve.
- Balance is key: A teaspoon of sugar and a splash of balsamic tame acidity without making the soup sweet.
- Handle basil gently: Tear, don’t chop, and add at the end to keep the flavor bright and the color vivid.
Variations
- Dairy-free/vegan: Swap heavy cream for 1/2 cup unsweetened cashew cream or full-fat coconut milk; use olive oil instead of butter.
- Roasted red pepper twist: Blend in 1 cup jarred roasted red peppers (drained) for a smoky-sweet note.
- Spicy arrabbiata: Add 1/2–1 teaspoon red pepper flakes and finish with extra-virgin olive oil instead of cream.
Storage & Make-Ahead
Refrigerate soup (without croutons) in an airtight container for up to 4 days. Croutons keep in an airtight container at room temperature for 3 days; re-crisp in a 350°F oven for 5 minutes. For longer storage, freeze the soup without cream for up to 3 months; thaw overnight, reheat gently, and stir in cream and fresh basil just before serving. You can also roast the tomatoes and caramelize the onions a day ahead to streamline dinner.
Nutrition (per serving)
Approximate values with croutons: 370 calories; 24 g fat; 33 g carbohydrates; 8 g protein; 4 g fiber; 750 mg sodium. Values will vary based on brands and exact measurements.
