Shrimp and Asparagus Pasta

Name: Shrimp and Asparagus Pasta
Ingredients: 12 ounces spaghetti; 3 tablespoons olive oil; 1 yellow onion , diced; 1 pound medium-large uncooked shrimp (21/25 per pound); 1 bunch medium-sized asparagus , tough ends removed, cut into 1-inch pieces; 4 cloves garlic , minced; 1/2 teaspoon kosher salt , plus more to taste; 1/4 teaspoon freshly ground black pepper , plus more to taste; 1/2 cup dry white wine; 3 tablespoons unsalted butter , divided; 1 lemon, juiced; 1/4 cup Parmesan , grated; 4 teaspoons flat-leave parsley, chopped; 4 lemon wedges