Preheat your oven to 450°F and line a baking sheet with parchment paper. Place the red peppers, onion, and garlic on the sheet. Drizzle with olive oil and sprinkle kosher salt over the vegetables.
Roast the vegetables in the oven for about 25 minutes, or until they are soft and lightly charred.
Boil salted water in a large pot and cook the penne pasta according to the package directions. Reserve 1/4 cup of the pasta water before draining.
Place the roasted vegetables in a blender. Add half-and-half, tomato paste, dried oregano, red pepper flakes, and an extra pinch of salt. Blend until the sauce is smooth and creamy.
Return the drained pasta to the pot along with the butter. Pour the blended sauce over the pasta and stir over medium-low heat for 3-4 minutes, adding reserved pasta water if needed to achieve the desired consistency.
Plate the pasta and finish with a generous sprinkle of grated Parmesan cheese and a sprinkle of basil, if preferred. Enjoy your meal!