Asian Peanut Butter Pork

2lbs pork tenderloin
1 onion, sliced in rings
1/4 cup soy sauce
3 tablespoons white wine vinegar
3 tablespoons water
2 garlic cloves, chopped
1/2 cup creamy natural peanut or other nut butter
2 tablespoons chopped peanuts (garnish; optional)
1 lime, cut in wedges (garnish; optional)

Use a 4-6 quart crockpot. Put onion slices into the bottom of your crockpot. Put the pork on top. Add soy sauce, vinegar, water, garlic, and peanut butter. No need to stir--the peanut butter needs to melt before you can do so. Cover and cook on low for 6 hours, or on high for 4. The pork will be more tender the longer you cook it. 1 hour before serving, flip the meat over in the crockpot to allow the other side to soak up the peanut-buttery goodness. Garnish with chopped peanuts, and serve with steamed rice and lime wedges.