In a large mixing bowl mix the masa harina, salt, and onion powder. Gradually add the hot water and stir with a wooden spoon. Use your hands to knead the dough until it forms a smooth, cohesive ball (1-3 minutes). You should have a smooth, springy dough, add water or more masa flour to adjust if necessary.
Using a spoon to portion the dough into a 2-Tbsp ball (about a golf ball in size) and roll into a ball.
Place the dough ball between two pieces of parchment paper on a tortilla press, then gently press until it forms a 5-6 inch tortilla.
Heat the skillet over medium-high heat. Cook the tortilla for 30-60 seconds per side, flipping as it heats, until you see small brown spots forming on the tortilla. You may need to flip and repeat several times per tortilla.
Transfer cooked tortillas to a tortilla warmer or under a kitchen towel to stay warm and keep from drying out. Repeat for all remaining dough.
Serve and enjoy.