Heat a large skillet over medium-high heat and add 1 tablespoon of olive oil. Slice the sausage into bite-sized pieces and sauté them in the hot skillet for about 5–7 minutes, stirring occasionally, until they turn golden brown and crispy on the edges. Remove the sausage from the skillet and set it aside.

In the same skillet, add more olive oil if needed and reduce the heat to medium. Add one chopped yellow onion and cook for about 3–4 minutes, stirring frequently, until the onion becomes soft and translucent.

Add sliced bell peppers to the skillet with the sautéed onion. Cook for an additional 5 minutes, allowing the peppers to soften and become vibrant in color.

Stir in 3 minced garlic cloves and cook for about 30 seconds, until fragrant.

Pour in a can of crushed tomatoes, followed by salt and black pepper to taste. Stir everything together, then reduce the heat to low and simmer for 10–15 minutes.

While the sauce simmers, bring a large pot of salted water to a boil. Add the penne pasta and cook according to package instructions, usually around 9–11 minutes. Reserve 1/4 cup of the pasta water before draining.

Add the cooked penne pasta to the skillet with the sauce and sausage. Toss gently to combine, adding reserved pasta water as needed.

Plate the pasta while hot, and sprinkle with fresh parsley if desired. Serve immediately.