Make the spice blend: stir together salt, paprika, garlic powder, black pepper, and cayenne. You'll use half in the buttermilk and half in the flour.
Slice each chicken breast in half lengthwise to make 4 thinner filets.
Place chicken in a large zip-top bag. Whisk half the spice blend into the buttermilk, pour over the chicken, seal, and coat every piece. Refrigerate 2 to 3 hours (or longer).
Stir the remaining spice blend into the flour. Take chicken straight from the buttermilk and dredge in the seasoned flour, turning to coat well.
Let the breaded chicken rest 15 to 20 minutes so the coating adheres.
Melt the lard in a cast iron skillet over medium heat and bring to 350°F.
Gently add the chicken. Hold the temperature near 350°F, frying several minutes per side and flipping once or twice, until the internal temperature reaches 165°F (about 12 minutes total).
Drain briefly and serve on its own or on a toasted bun.