Mix dry: In a bowl, combine flour and baking powder (add salt if using).
Add fat: Rub in butter/shortening until the mixture looks like fine crumbs.
Add liquid: Pour in warm milk (or water) gradually, stirring with a fork until a soft, non-sticky dough forms.
Knead: Turn onto a lightly floured surface and knead 3–4 minutes until smooth and springy.
Rest: Cover and let the dough rest 15 minutes (gluten relaxes; easier rolling).
Divide: Cut into 10 equal pieces; roll each into a smooth ball. Keep covered.
Preheat pan: Heat comal/skillet over medium for a steady, even heat.
Roll: On a lightly floured surface, roll one ball into a 7–8 in (18–20 cm) disc, about 1–2 mm thick; dust off excess flour.
Cook: Place on hot pan; cook 20–30 sec until bubbles and light spots appear. Flip and cook 20–30 sec more; flip once again 10–20 sec, gently pressing to encourage puffing.
Keep warm & repeat: Stack cooked tortillas in a towel to stay soft. Repeat with remaining dough. Serve warm.