Preheat a medium sized skillet over medium heat. Brown the bacon slices on each side until they are just crisp. Remove them from the pan and set them aside on paper towels. Cut them in 2.
Spread 4 slices of bread with mayonnaise then cover with cheddar cheese. Add a few pinches of cayenne pepper, and season to taste with onion flakes, salt and pepper. Top with tomato slices, then bacon.
Garnish with spinach leaves, then cover with the remaining slices of bread, previously spread with mayonnaise.
Serve immediately with BBQ ripple chips.