Tempeh-Stuffed Bell Peppers

1 cup brown basmati rice

1/2 cup plus 1 tablespoon extra-virgin olive oil

10 large fresh plum tomatoes

4 large red bell peppers, tops cut away and seeded

1/2 cup finely diced yellow onion

1/2 cup finely diced red onion

1/2 cup finely diced green bell pepper

1 pound tempeh (8-ounce packages), crumbled

1/2 teaspoon ground cumin

1/4 teaspoon red pepper flakes

1/8 teaspoon cayenne pepper

10 roasted garlic cloves

1 tablespoon red wine vinegar

1/4 cup minced fresh thyme, plus more for garnishing

Freshly ground white pepper