In a large skillet over medium heat, heat the olive oil. Add the beef and cook until it is no longer pink. Add the onion, garlic, bell pepper, jalapeno peppers (if using), chili powder, cumin and salt and pepper to taste. Cook until vegetables are soft.
Remove from heat and let cool slightly. Preheat oven to 375°F.
On a lightly floured surface, roll out the pastry dough into a 12-inch circle. Using a 4-inch cookie cutter or glass, cut out 12 circles.
Fill each circle with about 2 tablespoons of the beef mixture. Fold in half and press edges together with a fork to seal.
Place empanadas on a baking sheet lined with parchment paper. Bake for 15 minutes or until golden brown.