In a microwave-safe bowl or ramekin, combine chopped apple, cinnamon, vanilla, and lemon (and optional sweetener if using). Stir to coat.
1 small apple, ¼ tsp cinnamon, ⅛ tsp vanilla extract, 2 tsp lemon juice, 1 pinch allspice, ½ tsp maple syrup
Microwave for 1½–2 minutes, or until the apples begin to soften.
While the apples cook, mix all topping ingredients in a small bowl until crumbly.
1 tbsp rolled oats, 1 tbsp almond flour, 1 tsp flaxseed, ½ tsp cinnamon, 1 pinch salt, 1 tsp olive oil, 1 tsp walnuts
Carefully remove the bowl from the microwave. Spoon the oat topping over the apples.
Microwave for another 30–60 seconds until the topping is warm and slightly crisped.
Let cool for 1–2 minutes. Serve as is, or top with a dollop of plain Greek yogurt or a splash of unsweetened almond milk.