Preheat your oven to 425°F and line a baking sheet with parchment paper.
Pat the chicken breast dry and cut it into bite-sized pieces or thin strips as preferred.
In a shallow dish, combine the almond flour with a pinch of salt and pepper.
In a separate bowl, whisk the egg white until frothy.
Dip each piece of chicken into the egg white, then coat evenly with the almond flour mixture.
Arrange the coated chicken pieces on the prepared baking sheet in a single layer.
Bake in the preheated oven for about 18-20 minutes, or until the chicken is fully cooked and lightly crisp.
While the chicken bakes, prepare the sweet and sour sauce by mixing the pineapple chunks, rice vinegar, honey, and ketchup in a small saucepan.
Heat the sauce over medium-low heat, stirring occasionally, until it slightly thickens and the flavors meld together, about 4-5 minutes. Optionally, add the red bell pepper slices for extra flavor and crunch.
Once the chicken is done, drizzle the sauce over the baked pieces or serve on the side for dipping.
Garnish with additional pepper slices or pineapple if desired and serve immediately.