Heat the olive oil in a large deep skillet or Dutch oven over medium-high heat. Add the sausage and cook, breaking it into bite-size crumbles, until deeply browned and cooked through, about 5–6 minutes. It must reach 165°F — browning the sausage first builds the flavor base for everything that follows. Transfer to a plate, leaving the drippings in the pot.

Add the onion and bell peppers to the pot and cook, stirring occasionally, until softened and lightly charred at the edges, about 4–5 minutes. Stir in the garlic, Italian seasoning, and red pepper flakes; cook 1 minute more, until fragrant.

Pour in the crushed tomatoes and chicken broth, scraping up any browned bits from the bottom — that's flavor. Stir in the uncooked penne and bring to a lively simmer.

Reduce the heat to medium-low, cover, and cook until the penne is al dente and most of the liquid is absorbed into a glossy sauce, about 11–12 minutes. Stir two or three times so no noodles stick.

Uncover, stir the sausage back in, and cook 1–2 minutes to heat through. Take the pot off the heat and stir in the Parmesan until melted and the sauce turns creamy.

Spoon into warm bowls and finish with fresh basil and extra Parmesan.