Preheat the oven to 375°F.
Spray a muffin tin with cooking spray or line the tin with paper liners.
In a small bowl, mix the flour, baking powder and salt together, then set aside.
In a separate bowl, combine the brown sugar, butter, eggs & vanilla and whisk until smooth. Mix in the dry flour mixture a couple tablespoons at a time, stirring together until completely incorporated.
When all the flour has been mixed in, add the mashed bananas and the quinoa, and mix well. Add the chopped strawberries and fold into the muffin batter.
Divide the batter among the prepared muffin cups.
Place one strawberry slice on top of each muffin, and bake for about 25-30 minutes, until a toothpick inserted into the center of one of the muffins comes out clean.
Remove from oven and cool for a couple of minutes before removing muffins from pan.
Cool on a rack for about 10 minutes, or until ready to serve.