Add oil to a cast iron skillet and heat over medium-high heat. Season roast with salt and pepper. Sear roast in hot pan on all sides. Remove to a crock pot.
Add onion around the roast. Sprinkle in the Kinder's and McCormick's seasonings. Add broths. Cover and slow cook on LOW for 8 hours.
Remove beef from the broth and shred into small pieces.
Heat a large skillet over medium heat.
Dip the tortillas into the liquid mixture in the crock pot. The fat will be on the surface, so you don't need to dip it too far in. Just make sure it's covered good.
Top half of the tortilla with shredded beef, onions if desired, cilantro and shredded cheese. Fold over and fry your taco in a non stick skillet over medium heat until crispy, about 2 minutes per side.
Serve with a side of the stew to dip your taco in.