01 -
Bring a large pot of water to a boil with salt. Cook the pasta until al dente, reserving half a cup of pasta water before draining.
02 -
Heat olive oil in a skillet over medium high heat. Cook the sliced kielbasa until browned on both sides, then remove to a plate.
03 -
Add diced onion to the skillet and cook until translucent. Add garlic and sauté briefly, then add bell peppers if using and cook until softened.
04 -
Return the kielbasa to the pan, add cooked pasta and sauce. Stir to coat, adding reserved pasta water if needed to loosen.
05 -
Season with salt, pepper, and red pepper flakes. Let simmer for 5 minutes to blend flavors and thicken sauce.
06 -
Turn off the heat, top with cheese, and let it melt. Garnish with fresh parsley and serve immediately.