Mix in the diced onion and stir, then add the olive oil and vinegar, stir, and set aside.
Melt the butter and stir in the hot sauce. Add the shrimp in a single layer and cook until they just turn pink, flipping shrimp halfway through then cooking them until they curl slightly, 2 to 4 minutes total depending upon their size.
To serve, fill place 3-4 shrimp on each tortilla and with and top with two tablespoons of orange & grape salsa, a generous sprinkling of feta cheese and basil.