Buy shelled and deveined shrimp, and this recipe is as fast as dinner gets. Be sure to zest the lemons before you juice them.
Drizzle 1 tablespoon olive oil into boiling salted water. Add linguine, and cook according to the directions on the package, 7 to 10 minutes.
While the pasta is cooking, place the butter and the remaining 5 tablespoons olive oil in a large, heavy-bottomed pot set over medium heat. Once butter has melted, add the garlic and saute until lightly brown, about 2 minutes, being careful not to let it burn. Add the shrimp, parsley, salt, and pepper, and saute, stirring occasionally, until the shrimp have just turned pink, about 5 minutes. Turn off the heat.
When the pasta is done, drain the cooked linguine, and add immediately to the shrimp. Add the lemon juice, pepper flakes, lemon slices, and lemon zest. Toss well, season to taste, and serve immediately.