Preheat oven to 375°F.
Slice about a third of the bread and measure5oz., set aside for gazpacho.
Slice the remaining bread and set aside for crostini.
Gazpacho: add 1 Tbsp. of olive oil in Sauté pan over medium heat, add onion slices (cut side down) and garlic cloves. Cook until both sides are black (burned) then remove from heat and setaside in a bowl, place in cooler
Rub 5 lbs. tomatoes (set aside the rest for crostini) with olive and salt, place on sheet tray with parchment, stem side down and nestled together so that all of the tomatoes are touching. Roast for 1 hour.
Remove tomatoes from oven to cool slightly, then place in the cooler until completely cooled (about 30 minutes).
Place cooled roasted tomatoes, onions, garlic, 5oz. of bread (diced) and 1 cucumber (diced) into blender and pulse until large pieces are broken up. Season with salt, olive oil and sherry vinegar. Pulse again (using low speed) until smooth. Check seasoning and adjust if necessary.
Crostini: dice remaining 2 lb. tomatoes, red onion, and parsley. Season with salt and olive oil, set aside mixture until ready to plate.
Plating: toast 2 pieces of bread at a time in 1-2 Tbsp. of butter until both sides are golden brown and crispy. Top each crostini with the diced tomato and red onion mixture, garnish with olive oil and sea salt flakes.
Pour gazpacho into stemless wine glass and garnish with olive oil and a pinch of microgreens.