Preheat oven to 325°F (160°C).

Cook string beans until tender.

Finely chop the onions.

Sauté the finely chopped onions and ground meat in butter for 20 minutes, or until meat is browned.

Add the cooked string beans to the meat mixture and cook slightly to combine flavors.

Add half of the salt, pepper, nutmeg, and sugar to the meat and string bean mixture.

In a separate bowl, beat the eggs slightly.

Add the remaining salt, pepper, nutmeg, and sugar to the beaten eggs and mix well.

Pour the beaten egg mixture over the meat and string bean mixture in the pan.

Add the lemon juice to the mixture and mix well to evenly distribute.

Grease the bottom of a 10-inch pie pan.

Pour the string bean mixture into the greased pie pan.

Bake in the preheated oven for 45 minutes, or until the casserole is set and lightly golden.