Grease a round baking tin (24 cm Ø; approx. 4 cm high). Knead 200 g flour, 60 g sugar, 100 g butter in pieces and egg first with the dough hooks of the mixer, then quickly with your hands to a smooth dough. Roll out the dough round (approx. 28 cm Ø) on a floured work surface. Line a mould with it. Cover and chill for approx. 45 minutes.
In the meantime wash, clean and chop the strawberries. Mix with jam sugar and lemon juice in a large pot. Bring to the boil while stirring and boil for about 5 minutes until bubbly. Let jam cool down.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Prick the bottom of the mould several times with a fork. Cover the dough with baking paper and place legumes on top. Pre-bake in the hot oven on the lowest shelf for about 20 minutes. Remove the paper with the pulses and bake the cake for 5-10 minutes. Remove from the oven and let it cool down on a cake rack.
Put the strawberry jam on the bottom and smooth it down. Chill for about 1 hour.
Mix gelatine and 150 ml cold water in a small pot. Leave to swell for about 10 minutes. Sieve the icing sugar into a bowl. Beat the egg whites until stiff, adding 1 pinch of salt and 2 tbsp. sugar. Put it in a cold place. Bring gelatine to the boil briefly and stir into the icing sugar. Whip for 4-5 minutes. Add 2 portions of beaten egg whites to the marshmallow mixture. Immediately spread it dome-shaped on the strawberry jam. Chill the pie for about 1 hour.
If you wish, lightly scarf the marshmallow meringue with a kitchen gas burner.