Combine yogurt and next 4 ingredients in a bowl. Crumble cornbread into crumbs, to yield 2 cups. Reserve remaining cornbread for another use. Fold cornbread crumbs and tuna into yogurt mixture. Form into 8 patties. Heat butter and oil in a large skillet. Cook patties, in batches, 2-3 minutes per side or until golden brown.
Lemon Yogurt Sauce
Combine all ingredients. Serve with tuna cakes.
Corn on the Cob
Shuck corn. Bring large pot of water to a boil. Boil corn 10 minutes. Serve with butter and salt, if desired.
Fresh Tomato Slices
Slice tomatoes. Serve with salt and pepper, if desired.