Preheat the oven to 350 degrees F.
Combine the masa harina and salt in a medium mixing bowl. Add 2 cups of room temperature water. Stir well to combine, then let sit for 5 minutes.
Form about 1 tablespoon of dough into a ball. Flatten it between your palms to form a ¼-inch patty. Carefully pat out any cracks and place on a parchment-lined baking sheet. Repeat with the remaining dough.
Heat 2 tablespoons of vegetable oil over medium-high heat in a large skillet or nonstick pan. Add the arepas to the pan (you will need to do this in 2-3 batches). Cook on each side for 4-5 minutes, until the arepa has formed a crust and is quite golden, adjusting the heat if it starts to burn on the bottom. Remove to the baking sheet. Repeat with remaining arepas, adding more oil as necessary.
Finish the arepas in the oven for 10 minutes. Cool enough to handle, then carefully slice each arepa in half to form two small disks. Top the bottom half with a scant tablespoon of spicy black beans, a small dollop of sour cream, and a sprinkle of queso fresco. Garnish with cilantro and serve either open faced (for double the yield) or top with the other half.