In a large skillet, melt 2 tablespoons of butter over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant, being careful not to burn it.

Add the asparagus to the skillet and cook for 3-4 minutes, stirring occasionally, until tender-crisp.

Push the asparagus to one side of the skillet and add the remaining 2 tablespoons of butter. Once melted, add the shrimp, salt, black pepper, and red pepper flakes (if using). Cook for 2-3 minutes on each side until the shrimp are pink and opaque.

Squeeze the lemon juice over the shrimp and asparagus, then sprinkle with lemon zest. Toss everything together to combine and heat through for another minute.

Remove from heat and garnish with fresh parsley before serving.