Preheat oil to 350 degrees Fahrenheit (deep fryer or skillet with oil)
Season tomatoes, on both sides, with salt and pepper. Let them sit aside for at least 5 minutes while the water starts to come out of them.
While tomatoes rest. Place flour, garlic powder, and Cajun seasoning in a shallow dish. In another shallow dish, beat the egg with the milk.
Pat the tomatoes dry and then dredge tomatoes through the flour, then the egg wash, and then back in the flour mixture.
Add only a few pieces to the fryer at a time, so they can cook evenly, about 3 to 5 minutes (depending on your deep fryer). Drain on paper towels.