In a large bowl, combine masa harina, flour, baking power and 1/2 teaspoon salt. Slowly add water until a soft dough is formed. Transfer dough to floured surface; knead by hand for 5 minutes until dough is smooth. Cover in plastic and set aside.
On a lightly floured surface, roll dough to 1/4 inch thick. Using cookie or biscuit cutter, cut into 2-1/4 inch circles. Re-roll remaining dough, as needed, to get 24 circles. Heat 10-inch cast iron skillet over medium heat until hot; add oil. Fry sopes about 5 minutes or until golden brown and edges are crispy; turning once. Transfer sopes to paper towel-lined plate. Season with salt and pepper, as desired.
Meanwhile, in a small sauce pan, combine beef, lime juice, orange juice, cumin, chile power, coriander, garlic powder and remaining 1/4 teaspoon salt. Heat over medium heat until hot, about 5 minutes. Remove from heat; stir in tomatoes and jalapeño peppers. Keep warm.
Top each sopes with beans then beef mixture. Garnish with cheese and cilantro, as desired.
Nutrition information per serving: 207 Calories; 124.2 kcal Calories from fat; 13.8 g Total Fat; 2.4 g Saturated Fat; 0 g Trans Fat; 6.7 g Polyunsaturated Fat; 3.4 g Monounsaturated Fat; 23 mg Cholesterol; 479 mg Sodium; 12 g Total Carbohydrate; 1.6 g Dietary Fiber; 10 g Protein; 1.6 mg Iron; 177 mg Potassium; 3 mg Niacin; 0.3 mg Vitamin B6; 0.6 mcg Vitamin B12; 1.9 mg Zinc; 11.2 mcg Selenium; 28.7 mg Choline;