1. Melt 4 tablespoons butter in a large heavy-bottomed skillet over medium heat. Add 3 cloves garlic and cook, stirring constantly, 1 minute. Add scallions and continue cooking, stirring, 1 minute more. Add tomatoes, chiles, cinnamon, cloves, cumin, and salt; stir to combine. Cook, stirring often, until sauce is slightly thickened, about 5 minutes.

2. Add fish to the pan in a single, even layer. Reduce heat to a low simmer. Cook until fish just begins to turn opaque, about 1 minute. Carefully turn fillets and continue cooking 1 minute more; remove from heat and let cool.

3. When fish is cool enough to handle, shred meat using your fingers. Remove any remaining bones and discard. If sauce seems too thin, drain some of the liquid and discard.

4. In another large skillet, heat remaining 4 tablespoons butter over medium heat until hot and bubbling. Add remaining 3 cloves garlic and cook, stirring, 1 minute. Add shredded fish and sauce; cook until heated through. Serve immediately with tortillas or tortilla chips.