Early in the day, remove the bread dough loaf from the freezer. Place it on a cookie sheet greased lightly with olive oil. Then lightly grease the loaf. Let it sit on your counter during the day while it thaws. While the day goes along, I periodically spray the loaf with olive oil spray so it doesn't get dry, but this is optional.
Sometime during the day you'll also want to caramelize your onion. This can be done as early as you want or even a day ahead. Slice your onion very thinly. Put 4 teaspoons of olive oil in a large sauté pan and heat the oil. Put in your onion slices. Heat the onion on high until the onion is starting the release juices. Then turn the heat to low and stir the onion pieces around, tossing. Cook on low for a few minutes and then turn the heat back up. Cook on high a few minutes and then turn onion pieces again and reduce heat. Your objective here is to cook the onion the best you can without browning it, but raise and lower the temperature to release the natural sugars in the onion. This is the caramelization process. If it starts to get a bit brown, don't panic. Next time you do it you'll be better at it. It's not an exact science anyway. After about 10 minutes you have your onion good and gooey. It's cooked. Add your brown sugar and cook a bit more until the sugar is mixed in. Add your balsamic vinegar. Stir and let cool. That's done.
When you are ready to serve your focaccia, turn your oven on to 400 degrees. Flip your focaccia over on your cookie sheet. The air will come out of your puffy, risen loaf and it will collapse. That's fine. Spread it out with your hands and make dimples in the dough with your fingers. You are spreading it to a misshapen form, probably an oval that will cover a size about 15 inches wide and maybe 10 inches high; kind of an-out-of-shape pizza. The dimples are a good sign that you've shaped your focaccia correctly.
Spread on your cheese. Now bake your focaccia at 400 degrees for 15 minutes until golden brown around the edges. While this is going on you are prepping the rest of your focaccia.
Take your tuna and put it whole in a small bowl and soak it in your tequila. You don't want to leave it in the alcohol more than 15 minutes or the liquor will start to cook the fish. This is a short process. Heat your grill. You can use a stove grill or your outdoor grill. Just before your focaccia comes out of the oven remove the tuna from the tequila and grill your tuna to your liking. Throw away the tequila. (I know, it's too bad, but it won't taste good and it's not good for you at this point.) If you like your tuna rare in the middle, grilling will only take about two minutes on a HOT grill. For most folks 4 to 6 minutes is more like it. You want it with nice grill marks on the outside and pink and moist on the inside.
In the meantime, peel your avocados, remove the pit (seed) and chop the green parts into chunks about one-half inch or less in size. Reheat your caramelized onions just until warm.
When the focaccia comes out of the oven, be ready to put the rest of the stuff on top. Put your avocado pieces on top of the dough. If some of them get kind of squished, that's fine. Then pile on the tuna cut into bite-sized pieces, and then the onions. Over the whole thing, drizzle back and forth the balsamic glaze. The amount you drizzle is up to you. I just go back and forth lightly like you'd do if you were icing a cinnamon bun or a coffee cake.
I served this creation on a cutting board rather than a platter, but you can do either. You can cut in advance or let the guests cut it. When you cut it, the beauty of the presentation will be gone, so consider letting them see it before it's cut. It's a very unique look to see the color stacked up. And it's not often you see tuna on a focaccia like this, so it's a surprise with the balsamic glaze drizzled all over. You'll pleasantly shock even the most jaded of gourmet guests. Have fun with it.
*To many, the balsamic glaze may be a new product. I just discovered it myself. I used to have to boil down balsamic vinegar to a syrup which was a tedious process. Now they sell the glaze already boiled down. I hope you can find it. If not you can boil down the regular balsamic vinegar until it's reduced to a syrup consistency. This just takes an extra step. You can also do that early in the day. It's worth the effort for an amazingly gooey, sweet taste!