Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.
Combine the spinach, cilantro and garlic in a food processor and pulse until finely chopped. Transfer to a medium bowl. Add the ground beef, ground turkey, milk, breadcrumbs, chili powder, egg, 2 teaspoons of the Worcestershire, 1/2 teaspoon salt and a few grinds of pepper. Combine the mixture well with your hands.
Whisk the vinegar and the remaining 2 teaspoons Worcestershire together. Divide and pat the meat mixture evenly into four 1-inch-thick football shapes. Arrange on the prepared baking sheet. Top each meatloaf with 3 slices of tomato and drizzle with some of the vinegar-Worcestershire sauce. Bake until the meatloaves reach an internal temperature of 165 degrees F, 18 to 20 minutes. Drizzle with more vinegar-Worcestershire sauce and top each with the Cheddar and continue to bake until the cheese is melted, about 2 minutes more. Blot the bottom of each meatloaf on a paper towel to remove excess moisture. Serve with a salad if you?d like.
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