To prepare the achiote paste, in spice mill or mini-jar blender, combine achiote and coriander seeds, salt, peppercorns, cinnamon, oregano, cumin seeds and cloves; process to a coarse powder.
Transfer spice mixture to small bowl. Add vinegar, garlic and flour; stir to combine. Let mixture stand overnight.
To prepare chicken, in gallon-size sealable plastic bag, combine prepared achiote paste, lime juice, grapefruit juice, orange juice and zest; add chicken. Seal bag, squeezing out air, turn to coat chicken. Refridgerate overnight, turning bag occasionally.
To prepare vegetables, in medium non-stick skillet, heat oil; add onions. Cook over medium heat, stirring frequently, 10-12 minute until onion is golden brown. Stir in peppers, remove from heat.
Preheat oven to 350. Line baking sheet with foil. Cut four 12 inch squares of heavy duty foil; spray with nonstick cooking spray (omit this if using banana leaves).
Drain chicken, discard marinade. On each prepared foil square (or banana leaf) place one quarter of the chicken, one quarter of the onion-pepper mixture, and one tomato slice. Fold sides over filling, crimping to seal. Place packets on prepared baking sheet; bake 20 min until chicken is cooked through. Let stand 10 min; open packets carefully.