Preheat your oven to 375°F (190°C) and prepare a baking dish by lining it with aluminum foil or a light spray of cooking oil.

In a large mixing bowl, combine flaked canned tuna, chopped red onion, sweet relish, mayonnaise, and honey Dijon dressing. Mix until well combined.

Gently fold in chopped baby spinach and shredded Mexican cheese blend into the tuna mixture.

Slice sweet peppers in half lengthwise and remove seeds. Arrange them cut side up in your prepared baking dish.

Fill each pepper half with the creamy tuna filling and top with half a slice of sharp cheddar cheese.

Bake for 30 minutes until peppers are tender and cheese is melted.

Broil for an additional 1-2 minutes until cheese is golden brown.