- On a plain surface dusted with flour, roll out pastry dough.
- Grease and line a 20x5-cm tart pan and keep it in refrigerator for 10 minutes.
- In a heavy based sauce pan, heat oil, add onions, salt and sugar. Cook for 20 minutes or until onions have caramelized with a golden color. Set aside.
- In a food processor, process the butter beans into fine puree.
- Pour it in a bowl, add Parmesan, Gruyere, eggs and season to taste. Mix well.
- Now pour this mixture over the pastry base, bake for 30 to 35 minutes at 180 C until surface is slightly golden in color.
- Leave to cool for 10 minutes.
- In a small bowl, mix chopped spring onions and cream together. Top baked tart with cream mixture and caramelized onions.
- Lima bean tart with caramelized onion is ready to serve!