Position a rack 6 inches from the broiler and heat to high. Halve the peppers lengthwise, remove stems and seeds, and place cut-side down on a foil-lined baking sheet. Broil until the skins are blackened and blistered all over, 12-15 minutes, rotating the pan halfway through. Immediately transfer to a bowl and cover tightly with plastic wrap. Let steam for 10 minutes - this loosens the skins so they peel right off.

Use your fingers to slip off the charred skins. Don't rinse under water - you'll wash away the smoky flavor. Roughly chop the flesh and set aside.

In a large skillet over medium heat, warm 2 tablespoons olive oil until shimmering. Add the onion with a pinch of salt and cook until softened and just starting to turn golden at the edges, 6-8 minutes. Add the garlic and cook until fragrant, about 30 seconds.

Stir in the tomato paste and cook, stirring constantly, until it turns a deep rust color and sticks slightly to the pan, 2-3 minutes. This caramelization builds serious depth.

Add the roasted peppers, broth, and red pepper flakes if using. Bring to a gentle simmer and cook for 5 minutes to marry the flavors. Transfer to a blender and puree until completely smooth, 1-2 minutes. Work in batches if needed and vent the lid to prevent steam explosions.

Return the sauce to the skillet over low heat. Stir in the cream and warm through without boiling, 2-3 minutes. Taste and adjust salt and pepper - the peppers vary in sweetness, so you may need more salt than expected. The sauce should coat the back of a spoon and taste balanced between sweet, smoky, and bright.

Toss with 12 ounces cooked pasta, or serve over grilled chicken, polenta, or roasted vegetables. Top with torn basil and grated Parmesan.