Preheat your oven to 425°F and line a baking sheet with parchment paper.
In a shallow bowl, mix the almond flour with a pinch of salt and pepper if desired. In a separate bowl, lightly whisk the egg white.
Dip the chicken breast into the egg white, then coat evenly with the almond flour mixture.
Place the coated chicken on the baking sheet and drizzle lightly with olive oil.
Bake the chicken in the preheated oven for 20-25 minutes, or until the chicken is cooked through and the coating is crisp.
While the chicken bakes, prepare the sweet and sour sauce by combining pineapple juice, low-sugar ketchup, rice vinegar, and cornstarch in a small saucepan. Heat over low-medium heat until the sauce thickens slightly, stirring constantly.
Toss the mixed vegetables with a little olive oil, salt, and pepper, and arrange them on a separate baking tray. Roast in the oven for 15-20 minutes until tender and slightly caramelized.
Once the chicken and vegetables are done, drizzle the sweet and sour sauce over the chicken or serve it on the side as a dipping sauce.
Plate the crispy baked chicken alongside the roasted vegetables, and enjoy your balanced, flavorful meal.