I used to know someone who was born in the 1910s and raised in Budapest, who made a filling for blintzes out of jam and ground walnuts.
I now know someone (unrelated to the first person) who was born in the 1920s and raised in Arad speaking Hungarian, who makes a filling for baked goods out of jam and ground walnuts.
So I guess that filling is an Hungarian specialty. What's it called in Hungarian? Google isn't helping, and the Arad person doesn't recall.
The combination is usually just named by its parts: diós-lekváros X "X with walnuts-and-jam" or lekváros-diós X "X with jam-and-walnuts". The jam is often apricot (baracklekvár), but prune butter (szilvalekvár) or any kind of fruit preserves will also work well. (OK, maybe not marmalade or hot pepper jelly. :-)
At its simplest, you spread your dough with jam, then sprinkle on the ground walnuts (what I think of as the glue method). Some recipes call for mixing jam and walnuts, often in equal proportion by weight, and then spreading it on the dough (which I think of as the mortar method). Some recipes mix other things (sugar, lemon zest, vanilla sugar, cinnamon) into the nuts first, and then use either of the two methods for applying the filling.
Dió lekvár (walnut jam). Usually made with green walnuts (Zöld dió lekvár). https://gasztroangyal.hu/receptek/zold-dio-lekvar/
