In the same pan, heat 2 tablespoons butter, the garlic, and chili flakes (to taste, we used 1/4 teaspoon) over medium heat. Cook for 30 seconds, until fragrant. Toss the drained pasta, lemon zest, Parmesan, broccoli, burst tomatoes, and ¼ cup pasta water into the pan and toss to combine. Cook, tossing, for 1-2 minutes, until the sauce thickens. Season generously with salt and freshly cracked black pepper.