Place tomatoes in a large cast-iron skillet. Add apple, onion, sugar, jalapeno, ginger, lemon zest and salt and pepper. Cook over low heat until thickened into a heavy paste, about 35 to 45 minutes. Transfer to a glass or ceramic bowl. Set aside to cool. Store in an airtight container in the refrigerator for up to 4 days. Just before serving, toss in the minced cilantro and season to taste with additional salt and pepper.