Heat 1 tbsp vegetable oil in a large skillet over medium heat.
Add the onion, green bell pepper, and garlic; cook, stirring, until softened and fragrant, 3β4 minutes.
Add the ground beef; cook, breaking it up, until lightly browned with no pink remaining, 5β6 minutes.
Stir in the carrot, potato, and tomato; cook 2 minutes to begin softening the vegetables.
Season the mixture with ground annatto (achiote), dried oregano, ground cumin, kosher salt (for filling), and black pepper; stir to coat.
Pour in 0.5 cup chicken broth, bring to a simmer, then cover and cook until the potatoes are tender and most liquid is absorbed, 8β10 minutes. Uncover and cook off excess moisture if needed; the filling should be moist but not wet. Spread on a plate to cool 15 minutes.
In a mixing bowl, combine the masa harina, ground annatto (achiote) (for dough), kosher salt (for dough), and vegetable oil (for dough).
Pour in the warm 2 cups chicken broth and mix with your hand until a soft, pliable dough forms that doesnβt crack when pressed; knead 1β2 minutes, then cover and rest 10 minutes.
Heat the vegetable oil (for frying) in a deep pot to 350Β°F. Line a sheet pan with paper towels or set a wire rack over it.
Divide the dough into 12 equal balls (about 2 ounces each). Working one at a time, place a ball between two pieces of plastic (a cut zip-top bag works) and press into a 4.5-inch disc. Spoon about 2 tbsp cooled beef filling onto the lower half, fold the dough over to form a half-moon, and press the edge to seal; crimp firmly so it wonβt open while frying. Repeat with remaining dough and filling.
Fry 3β4 pastelitos at a time, turning once, until deep orange and crisp, 3β5 minutes total per batch; cues: steady bubbling, the surface feels set, and the edges are lightly blistered. Drain on the rack and let stand 2 minutes to finish crisping.