Set an oven rack in the highest position and preheat oven to 425℉.
Place the bread onto a baking sheet and drizzle with olive oil. Bake until toasted, 5 to 7 minutes.
Meanwhile, in a large bowl add the tuna, mayonnaise, dijon mustard, garlic, celery, shallot, dill relish, pickled jalapeño, dill, and lemon juice. Stir to combine.
Once bread is toasted, divide the tuna salad mixture over the top of each slice. Next, add 3-5 slices of pickled jalapeno to each slice then evenly divide the cheese onto each. Place into the oven and bake for 5 to 8 minutes until the cheese is melted. Remove from the oven, top with additional dill and serve,