Jam bars with grated pastry topping

This familiar recipe goes back to my grandmother. I wrote it in my school cookery notebook as Grated Cookies, and there are countless variations online. It is easy to make and a good choice for beginners. If you have made it before, perhaps it is time to bake it again.
Adjust servings in the full version
Baking tray size 30*20 cm.
Melt margarine until liquid. Don't boil! Add sugar and stir. When the sugar has dissolved, add the eggs and mix until smooth. No need to beat.
Sift flour into a bowl, add salt and baking powder. Knead the dough. The dough turns out soft, elastic, forms well into a ball and does not stick to your hands at all.
Divide the dough into 2 unequal parts. We put the smaller part in the freezer (I also put the grater there so that it would cool down and the dough would be grated better).
Roll or press the larger piece of dough into the pan, forming a small rim around the edges.
Take any thick jam and spread it evenly onto the dough. I had apricot. I punched it a little with a blender and added a tablespoon of starch. Because it seemed to me that it was a bit runny.
Take the smaller piece from the freezer once chilled and slightly firm, but not frozen solid. Grate it directly over the jam, distributing it evenly.