In a small bowl, toss the red onion slices with a teaspoon or two of the champagne vinegar. Set aside while you work on the rest of the steps. This helps cut down on the harsh raw onion taste.
Slice the bread into ½-inch thick slices, drizzle with olive oil, sprinkle with a few pinches of salt, and grill both sides until lightly charred.
Remove the bread from the grill and rub it with the sliced side of the garlic clove while the bread is still warm.
Chop the bread into cubes and set aside.
Make the dressing: in another small bowl, whisk together the olive oil, vinegar, lemon juice, and pinches of salt, pepper, and red pepper flakes. Taste and adjust seasonings. Set aside.
In a large bowl, toss the bread cubes, tomatoes, onion slices, ricotta salata, and basil together with the dressing.
Top with the toasted pine nuts and a few more red pepper flakes.
Allow the salad to sit for 15-20 minutes for the dressing to soak into the bread. Taste and adjust seasonings.
Top plated servings with poached eggs if you wish.