Cut the steak into fajita strips and place in the slow cooker.
Slice the 2 limes in half and squeeze over the cut steak.
Add the chili powder, crushed red pepper, salt, and pepper.
Cook on low for 2 hours (or high for 1 hour).
When the meat has about 30 minutes left, cube the mango, grape tomatoes, and onion.
Mix the salsa ingredients in a bowl and add the chopped cilantro leaves.
Wash and dry the romaine lettuce leaves. Once the steak has finished cooking, add several pieces to each romaine leaf as well as the mango salsa.
This recipe is for 2 servings of lettuce wraps. Each serving will be 2-3 wraps depending on the size.Romaine, butter, or iceberg lettuce are good choices for the wrap. I do not recommend bitter lettuce varieties as they will clash with the steak and mango flavors.To lower the sweetness and the carb count, substitute the mango for avocado.Slow cooker beef can be stored in an airtight container in the refrigerator for 3-4 days.Beef and mango salsa leftovers can be kept sealed in the refrigerator for 1-2 days.