1. Rinse the quinoa several times.
2. Pour into a saucepan and add twice its volume of water.
3. Bring to a boil, reduce the heat and let cook for 10 minutes.
4. Meanwhile, cook the egg in a pot of boiling water for 10 minutes.
5. At the end of cooking, rinse the quinoa under water to cool it down, then drain the quinoa.
6. Wash and cut the tomatoes into pieces.
7. Finely slice the onions.
8. Chop the basil.
9. Peel the hard-boiled eggs.
10. Cut the feta into pieces.
11. In a salad bowl, mix everything together.
12. Serve.