Bring a large pot of salted water to a boil and cook the spaghetti until just al dente, about 8 minutes. Drain and set aside, reserving a little pasta water.
Heat olive oil in a large skillet over medium heat until shimmering and fragrant. Add the crushed garlic and cook for about 30 seconds until it releases a sharp, toasted aroma, stirring constantly to prevent burning.
Sprinkle in the red chili flakes and sizzle for another 10-15 seconds until you hear a faint crackle and see the oil turn a slight reddish hue, signaling the heat is unlocked.
Add the crushed tomatoes to the skillet, stirring well to combine with the garlic and chili. Bring the mixture to a gentle simmer, then reduce the heat to low and let it cook uncovered for 10-12 minutes, stirring occasionally, until the sauce thickens slightly and turns a vibrant ruby color.
While the sauce simmers, tear fresh basil leaves roughly and set aside. Taste the sauce and add salt gradually, adjusting to your preferred level of seasoning.
Once the sauce has thickened and smells fragrant with garlic and chili, turn off the heat. Mix in half of the torn basil, allowing its aroma to infuse the sauce.
Add the cooked spaghetti to the skillet, tossing gently to coat each strand evenly with the fiery tomato sauce. If the sauce feels too thick, loosen it with a splash of reserved pasta water, stirring until glossy and smooth.
Transfer the pasta to serving bowls, garnish with the remaining torn basil leaves, and finish with a drizzle of olive oil for extra shine and flavor. Serve immediately while hot and fragrant.
