Start by combining balsamic vinegar, pesto, honey, red pepper flakes, salt, and pepper in a bag or bowl. Add the chicken and let it marinate for at least an hour to soak up flavor. Grill over medium-high heat until fully cooked, then let the chicken rest for a few minutes before slicing.
While the chicken cooks, boil your pasta in salted water until al dente. Reserve a little pasta water before draining—this helps create a silky sauce later. Set the pasta aside while you prepare the tomatoes.
Heat olive oil in a large skillet and cook the garlic just until fragrant. Add cherry tomatoes and season them, letting them soften and release their juices. Stir in the basil and reserved pasta water, then toss the pasta in until everything is lightly coated.
Top the pasta with sliced grilled chicken. Add Parmesan, extra basil, and an optional drizzle of balsamic glaze. Serve immediately for the best flavor and texture.