Trim any thick connective tissue from the beef heart (or chosen cut). Cut into even 1–1.5 inch cubes so they cook uniformly. Pat dry with paper towels.

Make marinade

In a mixing bowl combine aji panca paste, red wine vinegar, soy sauce, minced garlic, ground cumin, smoked paprika, dried oregano, brown sugar, vegetable oil, salt, and black pepper. Whisk until smooth and homogenous.

Marinate

Place the meat cubes in a resealable bag or shallow dish. Pour the marinade over the meat, massage to coat all pieces, then refrigerate for at least 2 hours and up to 8 hours. Turn once halfway through if possible.

Skewer

If using wooden skewers, soak them in water 30 minutes before grilling to prevent burning. Thread 4–6 meat pieces per skewer, leaving a little space between pieces for even heat circulation.

Grill

Preheat a grill or grill pan to medium-high heat (about 425°F / 220°C). Brush grates with oil to prevent sticking. Grill skewers 2–3 minutes per side, turning to get even char and an internal temperature of about 135–140°F (57–60°C) for medium-rare to medium; longer if you prefer well-done. Baste with reserved marinade during the first minute of grilling only if marinade has not contacted raw meat (otherwise discard used marinade).

Rest

Remove skewers from the grill and let rest on a plate for 5 minutes to allow juices to redistribute.

Served With / Garnish

Prepare potatoes and corn

While the meat marinates or just before grilling, boil small potatoes in salted water until tender (15–20 minutes depending on size). If serving corn, boil or grill corn rounds until tender and slightly charred, about 8–10 minutes.

Plate and garnish

Arrange 1–2 skewers per person on a plate with boiled potatoes and corn. Spoon aji verde or chimichurri alongside, sprinkle chopped cilantro over the potatoes and skewers, and serve with lime wedges for squeezing over the meat.