Preheat oven to 425°F degrees. Place the Flexiflat on the Medium or Large Perforated Baking Sheet and set aside.
In the Stainless Mixing Bowl, stir together 1 teaspoon cumin, coriander, 1/2 teaspoon salt, 1/4 teaspoon pepper and 1 tablespoon of the oil. Place the pork tenderloin in the bowl and toss to be sure the pork is well coated with the spice and oil mixture.
Place the tenderloin on the Flexiflat and roast in the preheated oven until it registers 145°F on the Instant Read Thermometer when inserted into the center. Once pork is done cooking, transfer to a cutting board and let rest for 10 minutes before slicing.
Meanwhile, heat remaining oil in a skillet over medium heat. Add the onions and cook covered, stirring occasionally, until soft, about 15-20 minutes. Careful not to brown the onions, you just want them tender.
While the pork & the onions are cooking, chop the cilantro in the Eco-Chop and set aside.
Finely chop one of the tomatoes (you will add one tomato to the onion mixture and the other two will set aside to be used to top your tacos with) and set aside.
Once onions are finished cooking, add the 1 chopped tomato, the minced chipotle en adobo, remaining cumin, salt and pepper to the onions. Stir to combine and sauté for 3 minutes until the tomato has softened. Remove from the heat and stir in the vinegar and half of the cilantro.
After the pork has rested for 10 minutes, slice the pork thinly and cut the slices in half.