Cut tempeh into cubes and place into a flat container for marinating. Combine the ingredients for the marinade in a small bowl and whisk. Pour the marinade over the cubed tempeh and marinate overnight, or at least 2 hours.
Set the oven to 375 degrees and line a baking pan with parchment paper.
Heat a cast iron skillet over medium heat for 5 minutes. Once it is hot, add 2 tbsp of olive oil, sliced onion and garlic salt to the skillet. Cook for 7 minutes until the onions are soft and starting to brown (turn down the heat if beginning to burn). Add the sliced bell pepper and cook an additional 5 minutes until they begin to soften but remain bright.
Reserving the marinade, remove just the tempeh and spread it on the baking sheet. Bake in the oven for 30 minutes, adding the beans and reserved marinade, halfway through (coat well before placing back in the oven).
While the tempeh and beans cook, combine the avocado, cilantro, coconut milk, salt, garlic, lime juice and water in a blender. Blend until smooth, and check the taste and consistency, making any liquid or flavor adjustments necessary. Transfer avocado crema to a small bowl or gravy boat for serving.
When the tempeh and beans are finished cooking, transfer them to a serving bowl. Turn the oven off, and throw away the parchment paper on the pan. Add your tortillas to the sheet pan and place back into the cooling oven just a few minutes prior to eating, to warm them.
Sprinkle fresh cilantro over top of the tempeh and beans, and serve!