Step 1

Using wet hands, roll masa dough into 15 golf-ball-sized balls. Place balls on a baking sheet and cover with a moist towel. Working with one ball at a time, use your thumb to press a deep indent into the ball, then use your hands to work it into a small "bowl" with a 1/4-inch-thick edge.

Step 2

Place about 1 heaping tablespoon refried beans into the bottom of the "bowl," then top with about 1 heaping tablespoon shredded cheese. Using moist fingers, carefully bring dough edge together, enclosing the filling within, and press to seal. Roll the ball in your hands to return it to a uniform ball shape. Carefully pat pupusa down into a flat round about 4 inches wide and about 3/4 inch thick; if edges crack, run a wet finger around them to smooth them. Place pupusas on a baking sheet and keep covered with a towel as you work. Repeat with remaining masa balls and fillings.

Step 3

Lightly coat a large cast iron skillet with oil and heat over medium heat until shimmering. Working in batches, add pupusas and fry, turning once, until well-browned and crisp, about 4 minutes per side. Drain pupusas on a paper towel-lined plate, than transfer them to plates and top with curtido. Serve with hot sauce and lime wedges, if desired.