In a fine-mesh sieve, rinse the frozen peas under hot water until they are no longer cold to the touch. Shake off the water and transfer to a medium bowl. Add the buttermilk and 1 tablespoon of the salt, stir, and set aside for 1 hour.
In a medium saucepan set over medium heat, heat 2 inches of oil until it reaches 350° on a digital thermometer.
Meanwhile, in a medium bowl, combine the flour, semolina, Old Bay and cayenne pepper. Drain the peas through a colander or sieve, shaking the beans to remove the excess liquid. Turn them out into the seasoned flour and toss to coat.
Use a slotted spoon to remove the peas from the flour, tapping them to remove extra flour, and add the seasoned peas to the hot oil. Fry until golden brown, 4 to 5 minutes. Use a slotted spoon to transfer the fried peas to a paper-towel-lined plate and immediately season with the remaining 1 teaspoon of salt. Serve warm.