In a small bowl, combine the paprika, cumin, garlic powder, and 1 tsp of brown sugar.
Slice or shred the leftover turkey meat and place it in a medium sized mixing bowl. Add the orange juice and seasoning mixture. Mix until combined.
Heat 1 tbsp of olive oil in a large pot (I use my dutch oven) over medium-low heat. Add the seasoned turkey and sliced onion. Simmer, covered, for 30 minutes, stirring occasionally. Turkey meat should be soft and tender. Shred into smaller pieces if needed before pan frying.
Heat a large cast iron with 2 tbps of olive oil on medium-high heat until oil is shimmering. Add turkey and onions and sprinkle with remaining sugar. Cook until turkey is browned and crispy, about 12-15 minutes, turning once every 5 minutes.
Divide the turkey carnitas between tortillas and top with red onion, cilantro, and cotija cheese.
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Notes
For the orange juice, I always prefer fresh squeezed with no pulp but whatever you have in the fridge is just fine!