Cook the pasta
Bring a large pot of generously salted water to a boil. Cook the capellini according to package directions until just al dente.
Reserve about 1 cup of the pasta water before draining.
In a large skillet over medium heat, warm the olive oil. Add garlic and red pepper flakes and cook for about 30 seconds—just until fragrant.
Don’t let the garlic brown. Gentle is the goal.
Add the tomatoes, balsamic vinegar, salt, and black pepper. Bring to a gentle simmer, then lower the heat and cook 15–20 minutes, stirring occasionally, until the sauce thickens slightly but still feels fresh and light.
Add the drained pasta directly to the skillet. Toss gently to coat. If needed, add a splash of reserved pasta water to loosen the sauce and help it cling to the noodles.
Finish with basil
Stir in the fresh basil right at the end—this keeps it bright and aromatic.
Serve immediately
Top with extra basil, freshly grated Parmesan, and maybe an extra drizzle of olive oil if you’re feeling fancy.