Preheat oven to 375 degrees. Slice the bread loaf into 7 slices. Place on a baking sheet, and toast in the oven until lightly browned, about 7 minutes.
While the bread is cooking, prepare the pesto: Combine the avocado, olive oil, basil, baby spinach, pistachios, nutritional yeast, lemon juice, garlic, sea salt and pepper in a food processor. Pulse until well combined and mostly smooth. You may need to scrape down the sides once or twice to get everything well incorporated.
Once the bread is done cooking, transfer the slices to a serving dish. Spread the pesto onto the bread.
Place the tomato slices onto the crostini, sprinkle seat salt on top, and drizzle the balsamic glaze. Enjoy immediately!
Notes
*You can sub in grated parmesan cheese if you choose.