Steps
1. In a microwave-safe mug, melt the butter.
2. Add the egg and sugar; whisk until combined.
3. Stir in the flour, baking powder, and salt to form a smooth batter.
4. Fold in the diced strawberries gently.
5. Microwave on high for 1 minute 30 seconds to 2 minutes until the cake has risen and is set.
6. Let it cool slightly before enjoying.