In a small bowl, whisk together the balsamic vinegar, olive oil, salt, sugar, black pepper, cumin, and chopped cilantro.
Place the shredded cooked chicken in a bowl and pour the marinade over it. Toss to coat and let marinate for at least 15 minutes.
Preheat your oven to 400°F (200°C).
Arrange the flour tortillas on a baking sheet and lightly brush each with olive oil. Bake for about 5-7 minutes until golden.
Layer each tortilla with marinated chicken, black beans, corn, red pepper, jalapeno, and green onions.
Top each tostada with shredded cheese and bake again for 10 minutes until cheese is bubbly.
Top with shredded lettuce, salsa, sour cream, diced tomatoes, and cilantro before serving.
