Start by patting the shrimp dry with a paper towel. This is a crucial step to ensure they sear properly rather than steaming. Season both sides of the shrimp generously with salt and black pepper.
Heat the olive oil and 1 tablespoon of butter in a large skillet over medium-high heat. Once the butter is melted and bubbling, add the shrimp in a single layer. Cook for about 2 minutes per side until they turn pink and opaque. Remove the shrimp from the pan and set them aside on a plate.
In the same skillet, lower the heat to medium and add the remaining 2 tablespoons of butter. Once melted, add the minced garlic and sauté for about 1 minute. Be careful not to burn the garlic; you just want it to be fragrant and golden.
Stir in the fresh lemon juice and the red pepper flakes. Scrape the bottom of the pan to release any flavorful browned bits. This creates a light, zesty sauce in seconds.
Add the cooked shrimp back into the skillet. Toss them well to ensure every shrimp is coated in the lemon garlic butter sauce. Garnish with fresh chopped parsley and serve immediately while hot.