two 6-ounce tuna steaks, each 1 inch thick
1 1/2 tablespoons olive oil plus additional oil for brushing
1 tablespoon fennel seeds
1 1/2 teaspoons black peppercorns
1 medium fennel bulb (sometimes called anise, about 1 pound), trimmed and cut into 1/4-inch crosswise slices
1 medium red bell pepper, quartered and cut into 1/4-inch slices
2 large garlic cloves, sliced thin
1/2 cup water
1 tablespoon fresh lemon juice