Cook the pasta: Bring a large pot of salted water to a boil. Add the casarecce pasta and cook according to the package instructions, usually around 8-10 minutes, until al dente. Drain the pasta, reserving about 1/2 cup of pasta water for later use.
- Prepare the peperonata sauce: While the pasta is cooking, heat the olive oil in a large skillet or pan over medium heat. Add the sliced onion and bell peppers. Sauté for 8-10 minutes, stirring occasionally, until the vegetables are softened and beginning to caramelize.
- Add garlic and tomatoes: Stir in the minced garlic and cook for 1 minute until fragrant. Add the diced tomatoes (with their juices) and red wine vinegar. Season with salt and pepper to taste. Stir everything together, and let the sauce simmer on low heat for about 10-15 minutes, until the peppers are very tender and the sauce has thickened slightly.
- Combine the pasta and sauce: Add the cooked pasta to the pan with the peperonata sauce. Toss the pasta in the sauce, adding some of the reserved pasta water to help the sauce coat the pasta evenly. Stir everything together and cook for another 1-2 minutes to allow the flavors to combine.
- Serve: Plate the pasta and top with freshly chopped basil and grated Parmesan cheese (if using). Serve immediately and enjoy!