In a wide, shallow bowl, whisk together the flour, garlic powder, and 1/2 teaspoon each salt and black pepper. Lightly sprinkle the chicken all over with salt and pepper. Dip each piece of chicken in the flour mixture, shaking off any excess flour. (Set any leftover flour aside to use in step 3.)
In a large skillet with a lid, melt the butter over medium-high heat. Add the chicken and cook, turning occasionally, until golden brown all over, 8 to 10 minutes. Transfer the chicken to a paper towel-lined plate to drain.