A simple marinade ensures juicy, moist, tender, and flavorful chicken breasts every time. Leftovers can and should be used in different ways all week long!
Make the marinade and pour it into a large shallow container. Add the chicken breasts, turning to coat them well with the marinade. Cover and refrigerate from 12 to 24 hours.
Just before grilling, if making the salsa, roughly chop the red and yellow cherry tomatoes and place them in a medium-sized bowl. Add the olive oil, shallot, basil, thyme, and salt and pepper. Toss gently to combine.
Remove the chicken breasts from the marinade and pat them dry with pepper towels. Discard the remaining marinade.
Heat the grill to medium high. Carefully oil the grill rack.
Grill the chicken, turning once about halfway through the cooking time for simple grill marks on each side. Or, turn the chicken every two minutes or so a total of three times, so that you achieve cross-hatch grill marks (turn the chicken breasts a quarter turn as you flip them), until the chicken is cooked through, an internal temperature of 165°F.
Remove the chicken from the grill to a cutting board and let sit for at least 5 minutes before serving, sliced or whole. Serve with the tomato salsa if desired.
Notes
There should be no traces (or only the barest faint traces) of pink inside when the chicken is done, and an internal thermometer should read 165 F when an instant-read thermometer is inserted at the thickest part. If you are cooking chicken thighs instead (and those would also be delightful with this marinade), let the internal temperature come up to 170 F.