Bring a large pot of salted water to a boil. Cook the penne pasta according to package instructions. In the last 2 minutes of cooking, add the broccoli florets to blanch them. Drain the pasta and broccoli, reserving ¼ cup of pasta water, and set aside.

While the pasta is cooking, heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Season the shrimp with salt and black pepper, then sear for about 1-2 minutes per side until they turn pink and slightly crispy. Remove from the skillet and set aside.

In the same skillet, reduce the heat to medium and melt 2 tablespoons of butter. Add the minced garlic and red pepper flakes (if using), stirring for about 30 seconds until fragrant.

Deglaze the pan with the lemon juice, scraping up any browned bits for extra flavor. Add the sun-dried tomatoes and the reserved pasta water, stirring to combine.

Add the cooked pasta and broccoli back into the skillet, tossing to coat in the lemon garlic butter sauce. Stir in the remaining tablespoon of butter, lemon zest, and Parmesan cheese. Mix until everything is well incorporated.

Return the seared shrimp to the skillet, gently tossing to warm them through. Adjust seasoning with salt and pepper as needed.

Serve immediately, garnished with fresh parsley, extra Parmesan, and lemon wedges for an extra citrusy kick.