Cook the pasta in generously salted water until al dente (around 7-8 minutes). Drain the pasta but first reserve 1/2 cup of the pasta water.
While the pasta is cooking: Pat the shrimp dry with a paper towel and place them in a bowl. Add the onion and garlic powder, salt, and pepper and stir to combine. Heat the olive oil in a large skillet over medium high heat and add the shrimp and the minced garlic. Cook the shrimp on each side for 1-2 minutes until the shrimp are opaque and cooked through, adding the lemon zest towards the end. Be careful not to over-cook the shrimp. Remove and set aside.
Add the hot pasta, the pesto, a squeeze of lemon juice, and about 1/3 cup of the reserved pasta water. Use tongs to toss the pasta until well combined and the sauce takes on a creamy texture, adding a little more of the pasta water if needed. Taste and add more salt if desired. Top with the cooked shrimp, a few basil leaves for garnish, and serve immediately.