Pickle the shallots. Stir together the red wine vinegar, boiling water, sugar, and a pinch of salt until the sugar is dissolved. Pour the mixture over the thinly sliced shallots. Let sit at room temperature for at least 30 minutes.
Meanwhile, heat ½ cup olive oil with 4 cloves crushed garlic over low heat. Continue to gently simmer for 10 minutes or until the garlic cloves are browned and softened. Remove from heat and strain the oil, reserving the garlic for another use.
Pour ¼ cup of the garlic olive over the lightly toasted bread, tossing to coat. Season the bread with salt and pepper and set aside. Cool the remaining oil.
Whisk together the remaining garlic oil with the basil, parsley, oregano, lemon zest, lemon juice, balsamic vinegar, and a pinch of sugar until well combined. Season the dressing with salt and pepper.
Pour the dressing over the tomatoes, cherry tomatoes, and nectarines, gently stirring to combine. Let sit at room temperature for 10 minutes.
Portion the marinated tomatoes and nectarines into 2 plates. Top the fruits with the croutons, pickled shallots, and burrata and drizzle any extra dressing on top. Serve immediately.