Bring salted water to boil and cook pasta to al dente. Reserve ½ cup pasta water before draining.
Pat shrimp dry — wet shrimp steam instead of sear.
Heat olive oil in a large skillet over medium-high heat until shimmering.
Add shrimp in a single layer. Cook 1.5 minutes without touching until pink on the bottom. Flip and cook 1 minute more. The moment they're pink and curled into a C shape, they're done. Immediately transfer to a plate.
Reduce heat to medium. Add butter and garlic to the same pan. Cook 90 seconds until fragrant but not brown.
Add pasta and a splash of pasta water. Toss vigorously.
Return shrimp to pan, squeeze in lemon juice, and toss to coat.
Add another splash of pasta water if the sauce looks dry.