Heat 2 inches of vegetable oil in a large pot over medium-high heat until it reaches 375 degrees F.
In a shallow bowl, stir together the flour, cornstarch, half the chili powder, garlic powder, and half the lime zest.
Pour the buttermilk into a second shallow bowl.
Dip each pickle spear into the buttermilk, then coat it in the flour mixture. Place the coated spears on a plate.
Fry the spears in batches for 2 to 3 minutes until golden brown, turning once. Remove them with tongs and drain on a wire rack set over a sheet pan.
While the spears are still hot, sprinkle them with the remaining chili powder, remaining lime zest, and salt to taste.
Serve right away with lime wedges on the side.