Blend the spinach. Combine the 2 cups packed fresh spinach, 1/2 cup warm water, and 1/4 cup olive oil in a food processor or high-speed blender. Blend until smooth, scraping down the sides as needed.
Mix the dough. In a large mixing bowl, whisk together the 2 cups all-purpose flour, 1/2 teaspoon sea salt, 1/2 teaspoon garlic powder, and 1/2 teaspoon onion powder. Add the spinach puree and stir until a soft dough forms. If dry flour remains, add warm water 1 tablespoon at a time, mixing after each addition. It's better for the dough to be on the wet side and to use more flour during the rolling process.
Knead and rest. Turn the dough onto a lightly floured surface and knead for 2–3 minutes until smooth. Divide into 8 portions for large tortillas or 10–12 for medium tortillas. Roll into balls, cover with plastic wrap or a clean kitchen towel, and rest for 15–20 minutes.
Roll the tortillas. Heat a large dry skillet or comal over medium heat, adjusting toward medium-high as needed. Roll each dough ball into a thin, even round on a lightly floured surface with a rolling pin, using only as much flour as necessary to keep it from sticking. Keep the remaining dough covered. If using a tortilla press, flatten between parchment or food-safe plastic, then finish with a rolling pin.
Cook and cover. Remove any parchment or plastic before placing a tortilla in the skillet. Cook for 45–60 seconds, until bubbles and brown spots appear underneath. Flip and cook for another 15–20 seconds, or until no wet-looking dough remains, allowing approximately 1–2 minutes total. Stack the cooked tortillas inside a clean kitchen towel, keeping them covered so they stay soft.
