Cut the bread into cubes, about 1 inch in size. Slice the red onion thinly, the cherry tomatoes in half, and mince the garlic.
Heat up 2 tablespoons of the olive oil in a large skillet over medium heat. Add the bread cubes and cook until golden brown. Stir occastionally to prevent burning and to toast evenly on all sides. Remove and set aside.
Add the remaining 1 tablespoon of olive oil to the skillet. Add the red onions, tomatoes, minced garlic, and the spinach. Stir occasionally until the spinach is wilted. Stir in the toasted bread cubes and set aside.
In the skillet, fry the eggs until the eggs & yolks are cooked to preference. Add a drizzle more of olive oil if needed to prevent sticking while cooking the eggs.
Plate up the veggies and top each with a fried egg. Drizzle with a bit of the balsalmic vinegar.