In a medium bowl combine the flour, baking powder, baking soda, and salt. Stir to evenly distribute everything. Mixing all the dry ingredients ahead of time will reduce the amount of stirring needed and lead to more tender muffins.
In a large bowl, combine the sugar, apple sauce, and oil. Beat with a hand mixer on low speed (or a hand whisk) until smooth and well combined.
Add the oat milk, vinegar, and vanilla extract. Beat until combined.
Add the flour mixture and stir until just combined. Do not over mix.
Fold in the raspberries and rolled oats.
Scoop into prepared muffin wells, filling each with 1/4"/6mm space remaining.
Sprinkle the streusel mixture on each muffin.
Bake for 20-22 minutes until a skewer inserted comes out clean.
Allow to cool in the pan for at least 5 minutes before removing and allow to cool completely.
Serve warm or at room temperature. Best the same day. Store in the fridge for up to three (3) days and reheat before eating.