In a mixing bowl, combine masa harina and salt. Gradually add warm water, mixing until a dough forms. It should be soft but not sticky. If too dry, add a little more water; if too wet, add a bit more masa harina.

Divide the dough into 8 equal portions and roll each into a ball. Flatten each ball into a thick disc, about 1/4 inch thick.

Heat a non-stick skillet or griddle over medium heat. Cook each disc for about 1-2 minutes on each side until lightly browned and cooked through. Remove from heat and let cool slightly.

In a separate skillet, heat vegetable oil over medium heat. Carefully fry each cooked disc for about 1 minute on each side until crispy. Drain on paper towels.

Spread a layer of refried beans on each crispy sope. Top with shredded cheese, diced tomatoes, chopped onion, and cilantro.

In a small bowl, mix sour cream with ground cumin. Drizzle over the topped sopes before serving.