Put a large pot of water to boil over high heat. (The angel hair pasta will only take a few minutes so you can throw in the pasta when the shrimp is almost done.)
In another pot melt that butter with the olive oil over low heat. Once melted add in the lemon juice, garlic, and onions. Cook on low heat for about 5 minutes to infuse the the garlic-butter with flavor. Add the rest of the seasonings and bring to a low simmer.
Toss in the shrimp and cook until pink (about 5 minutes). In the meantime, drop in the pasta into the boiling water.
Once the pasta is cooked, strain and toss together with the shrimp and garlic-butter sauce. Serve.