In a large bowl, whisk the flour and salt together, then drizzle in the vegetable oil and rub with fingertips until the mixture resembles coarse crumbs.

Slowly add warm water while stirring with a wooden spoon until a shaggy dough forms; adjust water as needed.

Transfer dough to a lightly floured surface and knead for 5–7 minutes until smooth and slightly elastic.

Cover dough with a damp cloth and let rest for 10 minutes to relax gluten.

Divide rested dough into 8 equal balls; roll each ball into a 1/8-inch-thick circle using a rolling pin or tortilla press.

Heat a cast iron skillet over medium-high heat until a drop of water sizzles; cook each tortilla for about 1 minute per side until light brown spots form. Stack cooked tortillas under a towel to keep warm.

While tortillas cook, warm the refried beans in a small pot over medium-low heat for 5 minutes, stirring occasionally.

In a small frying pan, heat 3 tablespoons oil over medium heat; cook sliced onions 8–10 minutes, stirring, until golden and caramelized. Season lightly with salt.

If using ground beef, brown it in a skillet over medium-high heat for 6–7 minutes, breaking it up, then season with salt and pepper. If using cooked chicken, warm it through in the same manner.

To assemble, lay a warm tortilla flat, spread about 1/4 cup refried beans down the center, sprinkle with a handful of shredded cheese, add a spoonful of meat, and fold the tortilla in half. Top with fried onions, hot sauce, and cilantro; serve immediately.