If your pizza dough is currently in the fridge, remove from plastic bag and place in oiled bowl. Let it sit outside at room temperature while we prepare the other ingredients. Preheat oven to 450 degrees. Add sliced onions to large saute pan set to medium heat, along with balsamic vinegar and olive oil. Cook until softened and slightly caramelized, about 10 minutes. After they finish cooking, add a little salt, to taste. Place in separate bowl and set aside.
Add a little more oil to same saute pan and cook steak on medium- high. Once you get a good color on the bottom of the steak, flip it over to cook on the other side (about 5 minutes). Take steak off when it reaches 125 degrees. Place on cutting board and cover with foil for 5-10 minutes before slicing.
Slice mozzarella into 1/2 inch slices. Set aside. Add 1/4 teaspoon of Worcestershire sauce to 1 cup of marinara sauce. This will give it a deeper flavor that is perfect with the steak. Set aside
Grab a large baking sheet. Place room-temperature pizza dough on baking sheet. If it's slightly cool, that's ok. But it should not be straight from the fridge. Begin rolling out dough into an oval until it is the desired thickness. Use your fingers to place dimples all over dough. This will keep the center of the crust from rising too high during baking. Add a very thin layer of the prepared marinara sauce on top of the dough. You should be able to see the dough through the sauce.
Sprinkle 1/2 of the onions over the sauce. Place fresh mozzarella all over pizza. The slices should not be touching. Don't worry - it will melt and spread to fill the gaps. Bake pizza in preheated oven for 15-20 minutes, until the mozzarella just begins to bubble.
While pizza is baking, slice the steak into very very thin slices and re-cover with the foil.
Remove pizza from oven. Place sliced steak all over pizza. Top with the rest of the onions. Sprinkle with blue cheese crumbles. Place back in oven for 5 minutes, just to melt the blue cheese a little.
Remove from oven and drizzle pizza with balsamic glaze. Cut into 8 slices and serve! This pizza is messy so it's best to eat with fork and knife.