!For Fajita Seasoning:
In a small bowl, mix all ingredients together well. Set aside (or store in an airtight container until ready to use).
Heat oil in a 12-inch cast iron skillet over medium-high heat. Add onions and peppers. Cook, stirring occasionally, until onions and peppers are tender and browned, about 10 minutes. Remove onions and peppers to a large plate.
Add shrimp to the skillet, browning on one side, about 2 minutes, then flip. Sprinkle fajita seasoning over shrimp and return peppers and onions to the pan. Add 1/4c water to deglaze the bottom of the pan and create a saucy coating on the shrimp, peppers, and onions. Stir to combine. Add up to another 1/4c water if needed (you want it to be just barely loose, not runny). Cook until the whole mixture is steaming hot, another 1-2 minutes. Serve immediately.
!To Assemble Fajitas:
Take a hot tortilla, top with a generous amount of fajita mixture, squeeze of lime, followed by sour cream, cilantro, and hot sauce. Serve with lime wedges.