Preheat the oven to 350°F.
Slice the top off tomatoes and remove core. Scoop out the flesh and set aside, leaving a thick lining in the tomato. Place tomatoes in a baking dish.
In a bowl, mix together reserved tomato, lentils, onion, cumin, salt, pepper, vinegar, and parsley.
Fill each tomato with half the filling. Top with chopped pecans.
Place in the oven until tomato is softened, pecans are golden, and filling is warm, ~20 minutes