Bring a large pot of salted water to a boil. Add the 8 oz spaghetti and cook according to package instructions until al dente, usually about 8-10 minutes. Once cooked, reserve about half a cup of pasta water and then drain the spaghetti in a colander. Set aside.
While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the sliced red and yellow bell peppers. Sauté them until they begin to soften and develop a slight char, about 5-7 minutes.
Add the minced garlic and 1 teaspoon red pepper flakes to the skillet with the peppers. Stir and cook for about 1 minute until fragrant, but be careful not to burn the garlic. Next, add 1 cup sliced black olives, 1 tablespoon drained capers, and the entire can of diced tomatoes. Stir gently to combine all ingredients.
Lower the heat and let the sauce simmer for about 8-10 minutes. This allows the flavors to meld and the sauce to thicken slightly. Taste the sauce and season with salt and pepper as needed.
Add the drained spaghetti directly into the skillet with the sauce. Toss well to coat the pasta evenly. If the sauce feels too thick, stir in a splash of the reserved pasta water to loosen it up to your desired consistency.
Remove the skillet from heat. Tear fresh basil leaves and sprinkle generously over the top of the pasta. Serve immediately while warm.
