In the morning, spray a 4quart slow cooker with cooking spray. Trim the fat from the pork. Place in the cooker with tomatoes, cumin, chili powder, salt, and pepper. Stir to combine. Cover and cook on low-heat setting for 7 hours.
Shred meat using 2 forks. With a slotted spoon, top each tortilla with 1/4 cup pork. Divide the pineapple among the tacos. Save 2 cups leftover pork for Wednesday and freeze any remaining up to 3 months.
In a medium bowl combine lettuce, cilantro, and salad dressing. Serve with the tacos.