Prepare baking sheet with parchment paper and preheat your oven to 350F.
In a small bowl, whisk together melted butter, garlic, lemon juice, Italian seasoning and paprika.
Prepare your asparagus by washing, removing the ends and chopping into desired size. I chopped mine in half, but you could do thirds if you want smaller pieces. Slice onion if preparing your own. (I purchased pre-sliced)
Place shrimp, onion and chopped asparagus in a single layer onto the prepared baking sheet. Pour butter mixture on top and gently toss to coat. I used my hands for this step.
Place into oven and bake just until pink, firm and cooked through, about 10-14 minutes. Toss with a spatula or tongs halfway through, ensuring everything is evenly coated.
Serve immediately. Garnished with parsley and sliced lemons and limes, if desired. Add salt, pepper and more seasonings to taste.