Preheat oven to 375 degrees F.
Place crostini on sheet tray and brush each one with olive oil, season with salt and pepper. Bake until lightly browned, remove from oven, let cool.
In a large skillet sauté onions in olive oil until cooked through and lightly browned.
Add diced eggplant and sauté for 3-4 minutes.
Deglaze with red wine vinegar.
Add marinara sauce and water, bring to a simmer.
Season with salt and pepper. Cook until thickened and not watery. Remove from heat and let cool.
Once cool, top each crostini with 1 Tbsp. ricotta and a heaping Tbsp. of caponata mixture.
Garnish with parsley.