Lay the tomato slices on a paper towel-lined plate to absorb the tomato juices.

In a medium-sized bowl, combine the thinly sliced red onion with the minced garlic, 3 tablespoons of red wine vinegar, and kosher salt, toss to combine, and set aside.

Combine olives, capers, parsley, anchovy filets, and fresh oregano (or marjoram) in the bowl of a food processor. Pulse several times until the mixture is coarsely and evenly chopped. Add the olive and herb relish to the bowl with the onion and red wine vinegar. Give it a good stir and add 1/4 cup of olive oil. Stir in the olive oil and add the 2 tablespoons of Dijon. Mix well to fully combine and set aside.

Drain the oil-packed tuna (save the oil from the tuna to use in another dish). Slice the hard-cooked eggs into thin slices.

Use 2/3 of the olive herb relish/onion mix to evenly cover the bottom half of the baguette.

Then place the tuna evenly on top of the olive herb relish/onion mix. Pour the remaining 2 tablespoons of olive oil over the tuna. Shingle the tomato slices on top of the tuna. Then shingle the egg slices on top of the tomato. Use the remaining olive herb relish/onion mix to cover the eggs.

Top with the top half of the baguette.

Clear your work surface and stretch a large piece of plastic wrap, flat on the surface. Carefully slice the sandwich in half crosswise. We will wrap each half tightly in plastic wrap.

Place the halves side by side and place a sheet pan on top of the sandwich halves. Then place a Dutch oven or other very heavy pan on top of the sheet pan, positioned on top of the sandwich halves.

Let the sandwiches flatten for 30 minutes to one hour. Refrigerate the halves if you're planning to enjoy the sandwiches later. If you eat them right away, unwrap the sandwiches and place them on a paper towel to absorb excess liquid for a few minutes.

Slice each half in half again, if desired, and serve!