In a medium mixing bowl, add the tuna (drained) and using a fork break into small pieces. Add cream cheese, mayonnaise, mustard, horseradish, salt, and pepper. Mix thoroughly.
Add jalapeno, onions, artichoke, if using, and both cheeses. Fold in the ingredients evenly. Add the diced tomatoes and gently fold in until mixture is thoroughly combined.
Transfer mixture to an oven safe baking dish and spread out evenly. Allow for an uneven, peaked top of the dip. Sprinkle evenly with the extra Parmesan and paprika. Bake at 350 degrees for 20 minutes or until mixture is hot and bubbly (can be cooked in microwave for 1 minute, checking at 40 seconds). Serve warm or room temperature with crackers, crostini, pita bread or chips.