Add the dried chilies and cumin seeds to a small, heavy-bottomed skillet. Toast for 1-2 minutes over medium heat. Stir the ingredients constantly to avoid scorching. Remove the skillet from the heat when you can smell the cumin and the chilies have a few darker spots.
Add the chilies and cumin seeds to a large spice grinder or blender. Blend the spices into a powder. Add the tomato paste, cilantro, apple cider vinegar, maple syrup, oregano, and cinnamon to a blender. Blend until you have a smooth paste.
Line a baking tray with parchment paper or a baking mat. Set the oven to 425 F (220 C).
Cut the cauliflower into small, bite-sized florets. Add the florets to the bowl with the barbacoa paste. Use a spoon or your hands to coat the cauliflower with barbacoa. Place the florets, separated, in a single layer onto the baking sheet.
Place the cauliflower in the center of the oven. Bake for 15 minutes. Toss and bake another 5 minutes until they are tender. Use a fork to pierce a floret to check that they are tender. Keep them warm on low until you are ready for tacos.
To make the pepita sauce, grind the pepitas into a fine powder using a spice grinder or blender. Add the garlic, vinegar, and maple syrup to a blender. Blend until you have a smooth dressing with the consistency of sour cream. Add water, a tablespoon at-a-time, until you have a consistency you like.
Transfer the pepita dressing to a small bowl, then add the dill and black pepper.
Divide the cauliflower over 6 warm tortillas or wraps. Top with lettuce, tomatoes, red onions, or avocados. Tops with pepita dressing.