Preheat oven to 400 and line muffin tin with 11 paper cups (what? I'm precise!). Put diced strawberries into a bowl and sprinkle with lemon juice. In a bowl, combine flour, sugar and baking powder. In a 2nd bowl, mix together oil, sour cream, vanilla and egg. Combine wet and dry mixture and stir until incorporated. Add strawberries, leaving a small handful aside (about 1/2 cup). Pour batter into muffin tins. If you like them to puff nicely over the top, you'll need to fill them almost to the brim. Not overflowing, but just shy of the top. These don't rise much in the oven. Sprinkle the rest of the strawberry pieces on top and press very lightly. Bake for 17 minutes or until tester comes out clean. When cool, sprinkle powdered sugar lightly over top.