Preheat oven to 400°F. Stir 1½ cups rice and 2 cups water together in an 8-cup microwave-safe container; microwave on High until al dente, about 9 minutes, or 2 minutes less than the package directions. Drain and transfer to a large bowl. Add drained spinach, rinsed beans, ½ cup yogurt, 1 teaspoon lemon zest and ½ teaspoon salt; stir to combine.

Heat 1 tablespoon oil in a 10-inch cast-iron skillet over medium heat. Add 1 tablespoon garlic, 2 teaspoons each cumin, paprika and oregano and 1 teaspoon chiles, if using. Cook, stirring constantly, until fragrant, about 1 minute. Scrape the garlic and toasted spices into the rice mixture; stir to incorporate.

Heat the remaining ¼ cup oil in the skillet over medium heat. Add the rice mixture to the hot oil; use a spoon to flatten the mixture and cover the pan bottom. Use a wooden spoon handle to gently poke 4 or 5 holes in the rice layer (this will allow steam to escape and a crust to form on the bottom). Cook until the rice starts to sizzle, about 2 minutes. Transfer to the oven. Bake until the bottom is crisp, about 20 minutes.

Meanwhile, stir the remaining ½ cup yogurt, 1 tablespoon lemon juice and the remaining ⅛ teaspoon salt together in a medium bowl. Cover and refrigerate until ready to use.

Move the rice to fill in the holes. Arrange 6 cheese slices evenly on top of the rice mixture. Bake until the cheese melts, 2 to 3 minutes. Serve with the yogurt sauce.