Preheat the oven to 350 degrees Fahrenheit.

Mix margarine, sugar, egg, flour, and salt in a mixer until dough forms.

Chill in the refrigerator for one hour.

Press into mini tart pans (with removable bottoms) and bake for 20 minutes.

Let cool, then fill with custard and top with fruit.

For a sweet glaze, combine jam and water until smooth. Using a pastry brush, brush the top of the fruit with jam mixture.

These tarts can be assembled up to two days before serving. Tart shells can be made well in advance and frozen.