Season the beef evenly with 1 teaspoon each of salt, pepper and garlic powder all over. Set aside. Roughly chop the tomatoes, onion, garlic and chile peppers. Transfer them to the bottom of the slow cooker, season lightly with salt and pepper.
In a large skillet, preheat 4 tablespoons of avocado or olive oil to medium heat for 3 minutes. Sear and brown the pieces of beef for a few minutes per side. Add the the slow cooker as you cook them.
Add the chile ancho to some simmering water. Reduce heat and cook for 10 minutes. Drain all the water from chile ancho and transfer to the blender. Add 1 cup water or broth(if available), 1/2 teaspoon of salt, 1/2 teaspoon pepper, 1/2 teaspoon garlic powder, 1/2 teaspoon oregano and 1/2 teaspoon cumin. Blend on high until smooth. Taste for salt. Pour ancho sauce into slow cooker and stir to combine.
In that same pan that you browned the beef, add the red wine(or beer) to de-glaze the pan. Season lightly with salt and pepper, cook for a few minutes. Pour into slow cooker. Stir to combine. Cover and cook on for high for 4 hours on high or on low for 6 hours. Beef should be easy to shred with two forks. Before serving, remove beef from slow cooker and shred coarsely. Transfer beef back to slow cooker. Stir well to combine. Set to warm setting.
Before serving, remove beef from slow cooker and shred coarsely. Transfer beef back to slow cooker. Stir well to combine. Set to warm setting. Serve with warm tortillas and your favorite salsas, fresh or cooked.