In a small bowl, cover the ancho chile with hot water. Let soak until softened, about 20 minutes. Drain the chile, reserving 2 tablespoons of the soaking liquid. Halve, stem and seed the ancho.
In a blender, combine the garlic and ancho and blend until finely chopped. Add the curry powder, oil and the reserved ancho soaking liquid and blend until smooth. Blend in the yogurt. Transfer to a bowl and stir in the onion.
Any kind of beefsteak, lamb, chicken: marinate 8 to 12 hours.