To prepare chutney: Combine cherries, onion, sugar, vinegar, ginger, mustard seed, cinnamon, allspice, salt and pepper in a medium nonreactive saucepan (see Note). Bring to a boil over medium-high heat and cook, stirring occasionally, for 5 minutes. Stir in tomatoes and continue to simmer until they are cooked through and the liquid is slightly thickened, 3 to 4 minutes. Remove from the heat; cool, stirring occasionally, for 30 minutes.

To marinate pork: Place pork in a heavy-duty sealable plastic bag. Add 3/4 cup of the cooled chutney, chicken broth and 1 tablespoon oil. Seal the bag and turn to coat the pork with the marinade. Refrigerate the pork overnight. Refrigerate the remaining chutney.

To roast pork: Preheat oven to 425 degrees F. Remove the pork from the marinade, shaking off excess (discard marinade). Pat the pork dry with paper towels and season with salt, pepper and thyme.

Heat the remaining 1 tablespoon oil over high heat in a large ovenproof skillet until hot but not smoking. Add the pork and cook, turning until browned on all sides, 3 to 5 minutes.

Transfer the pan to the oven and roast the pork until just cooked through and an instant-read thermometer registers 155 degrees F in the center of the pork, 15 to 17 minutes. Transfer the pork to a cutting board and let rest for 5 minutes before slicing. Garnish the pork with cilantro, if using, and serve with the reserved chutney.

Tip: Be sure to measure frozen cherries while still frozen, then thaw. (Drain before using.)

Note: A nonreactive pan or container--stainless steel, enamel-coated or glass--is necessary when preparing acidic foods, such as cherries, to prevent the food from reacting with the pan or container. Reactive pans, such as aluminum or cast-iron, can impart an off color and/or off flavor in acidic foods.

MAKE AHEAD TIP: Cover and refrigerate the chutney (Step 1) for up to 3 weeks.