Put the hens on a cutting board, breast side down. Use kitchen shears to cut out the backbones. Open the hens to expose the ribs and then flip them breast side up. Use the palm of your hand to press down between the breasts to slightly flatten the hens. Put the hens in a large resealable zip-top bag, and then add the buttermilk, garlic powder, onion powder, cayenne, dried rosemary and 1 tablespoon salt. Shake well and refrigerate for at least 2 hours and up to 8.
About 2 hours before ready to serve, take the hens out of the refrigerator and let them marinate at room temperature for 1 hour.
Place a wire rack on top of a baking sheet. Fill a Dutch oven with 2 inches of oil and bring to 350 degrees F on a deep-fry thermometer over medium-high heat.
While the oil heats, remove the hens from the marinade and pat dry. Put the flour in a large, wide, shallow bowl with 1 teaspoon salt. Toss the hens to coat in the flour.
Put one of the hens in the hot oil, skin side down and reduce the heat to medium. Cover and cook for 5 minutes then uncover and cook for 5 minutes more. Turn the hen over and cook for 5 minutes. Flip and cook for 5 minutes more. Continue to cook, turning occasionally, until cooked through, up to a few minutes more. Carefully remove the hen from the oil and transfer it to the prepared baking sheet. Sprinkle with salt.
Return the oil to 350 degrees F and fry the other hen in the same way. Transfer the second hen to the prepared baking sheet and let them stand at room temperature for 10 minutes.