Bring a large pot of water to a boil. Add 1 Tbsp salt and 1 Tbsp olive oil, then cook the pasta according to package instructions until al dente. Drain the pasta, return it to the pot, and cover to keep warm.

In a large, deep pan over medium-high heat, add 1 Tbsp olive oil and 1 Tbsp butter. Add the asparagus, season lightly with 1/4 tsp salt and 1/8 tsp pepper, and cook uncovered for about 5 minutes or until crisp-tender, stirring occasionally. Remove the asparagus from the pan.

Using the same skillet, add 2 Tbsp olive oil and 2 Tbsp butter. Once the butter has melted, add the minced garlic and red pepper flakes (if using). Sauté, stirring frequently, for 1 minute. Add the shrimp in a single layer, and season with 1 tsp salt and 1/4 tsp black pepper. Cook until the shrimp are pink and no longer translucent, about 1 minute per side. Be careful not to overcook the shrimp to prevent them from becoming tough.

Add the lemon zest, lemon juice, and chopped parsley to the skillet, stirring to combine. Turn off the heat, then return the pasta and asparagus to the pan. Toss everything together until well combined. Serve with freshly grated parmesan.