First, make the sauce by mixing the sour cream with only the sauce from the can of chipotle peppers in adobo (you need 1 to 2 teaspoons [5 to 10 ml] of adobo sauce, depending on how spicy you want it).
Next, slice the bell peppers and onion into ¼-inch (6-mm)-widestrips. Make sure your shrimp is thawed and pat them dry with a paper towel.
Heat a large, cast-iron skillet over high heat. You want it to be smoking hot. Add the avocado oil, bell peppers and onion to the pan. Cook over high heat for about 5 minutes. Do not overstir the veggies, as you want them to char and get a nice color. Then, add the cumin, garlic powder, salt and shrimp to the pan. Stir to combine and sauté for another 3 minutes, or just until the shrimp curls up and turns opaque. Finish with the fresh lime juice.
Plate the fajitas with a drizzle of the chipotle sauce on top handsome chopped cilantro (if using).