In a large skillet, heat the olive oil over medium heat. Add the minced garlic and red pepper flakes, sautéing for about 1 minute until fragrant but not browned.

Pour in the crushed tomatoes and add sugar, salt, and pepper. Stir well and let the sauce simmer for 10-15 minutes, stirring occasionally.

While the sauce simmers, cook the spaghetti according to package instructions until al dente. Drain and set aside.

Season the salmon fillets with salt and pepper. In another skillet, heat a little olive oil over medium-high heat. Add the salmon, skin-side down, and cook for about 4-5 minutes. Flip and cook for another 4-5 minutes, or until the salmon is cooked through and flakes easily with a fork.

Once the sauce has thickened, add the cooked spaghetti to the skillet with the sauce and toss to coat.

Serve the spaghetti topped with the salmon fillet, garnished with fresh parsley and grated Parmesan cheese if desired.