1. Mix all the ingredients except the chicken in a large bowl.
2. Add the chicken to the mixture and coat evenly.
3. Cover the bowl and refrigerate for at least 4 hours or overnight.
4. Preheat the grill.
5. Remove the chicken from the marinade and discard the marinade. (This protects against cross-contamination.) Sprinkle the chicken with the salt and pepper.
6. Place the chicken on the hot grill and cook until the juices run clear, 6 to 8 minutes per side.
For the sizzle of corn and tomatoes:
1. Heat the oil in a skillet over medium heat. Cook the shallots for 2 to 3 minutes, until soft but not dark in color.
2. Add the tomatoes, corn and jalapeño pepper, and cook for 1 minute. Add the cumin and sugar and cook 1 more minute.
3. Add the vinegar and cook until the liquid reduces slightly.
4. Add salt and pepper to taste.
5. Spoon about 1/2 cup of the sizzle around the grilled chicken.