Let us cook chicken/ beef and onions. For this, take a skillet, add beef into it, and cook on medium heat. Break the beef into smaller pieces using a spoon and fry until it becomes brown. Remove the grease from the skillet, if any.
Add onions into the skillet and fry for two minutes. Now add chili powder, cumin powder, salt, and paprika into it and cook it for a few minutes until the raw smell goes.
Take the refried beans in a small skillet or a microwave bowl. Add one small scoop of sour cream into this and stir it continuously. Warm the mixture for a while.
It is time to assemble tostadas. For this, you can use corn tortillas and fry or bake them, or you can also use tostada shells.
To prepare the dish, start spreading a layer of refried beans mixture on the shell or tortillas. Top the tostada with a small spoon of beef, some lettuce, a little amount of cheese, salsa verde, avocado, sour cream, hot sauce, and salsa. Serve the dish hot.