Grilled SPAM®, Tomato, Cheddar Cheese, and Sweet Onion Sandwiches

Ingredients (7)

• + ¼ cup spicy brown mustard add to pantry
• + 8 slices whole wheat bread add to pantry
• + 1 (12 ounce) can fully cooked luncheon meat (such as SPAM®), cut into 1/4 inch slices add to pantry
• + 8 slices Cheddar cheese add to pantry
• ✓ 2 large tomatoes, cut into 1/2-inch slices
• + 1 sweet onion, thinly sliced add to pantry
• + ¼ cup softened butter add to pantry