Set oven temp to 350 degrees Fahrenheit.
Grease an 8 x 8 cake pan OR line it with parchment paper
Combine all the dry ingredients (the first five) in a large mixing bowl.
Make a well in the middle.
Combine wet ingredients (egg, oatmeal + vinegar, oat milk, and canola oil) in a medium bowl.
Pour the wet ingredients into the well in the dry ingredients bowl.
Add the strawberries and rhubarb.
Mix in the fruit gently, otherwise, you'll end up with pink coffee cake!
Stir until just moistened.
Pour batter into the cake pan with a spatula.
In a small bowl, combine the topping ingredients.
Sprinkle topping over the top of the cake batter.
Pop it in the oven.
After 30 minutes, use a cake tester or knife to ensure the center is set. (I just stick a butter knife in the middle).
Serve warm, or let the cake cool on a rack
Enjoy with whipped cream, vanilla ice cream, or just as a simple cake snack!