Step 1

In a large skillet cook the first five ingredients (through pepper) over medium until onion is tender, stirring occasionally. Coarsely mash bean mixture; cool slightly.

Step 2

Meanwhile, in a large bowl stir together flaxseed meal and ⅓ cup water. Let stand 15 minutes.

Step 3

Stir tomato sauce and soy sauce into flaxseed mixture. Add bean mixture, brown rice, and panko. Stir to combine. Divide into eight portions. Form into ¾-inch-thick patties.

Step 4

Grill, covered, over medium heat 5 minutes. Carefully turn burgers and grill 5 minutes more or until heated through. Brush with water if needed to prevent sticking. Serve burgers on buns with desired toppers.