Sift the flour. Place the butter in the freezer for 10-15 minutes and grate it on a coarse grater. To obtain the zest: rinse the lemon well, wipe it, then grate the top layer of lemon peel using a fine grater. Divide 1 egg into yolk and white (the white is not needed, use the yolk to grease the bagels). Lightly beat the yolk with a fork.
First, knead the shortbread dough. To do this, beat 1 egg into the sifted flour, add sugar, a pinch of salt, lemon zest, and grated butter. Knead well with your hands. If the dough is too dry, add 20 g of milk.
Place the finished dough in the refrigerator for 1 hour. Now start filling. Peel the bananas and cut into slices approximately 2-3 cm wide.
Lubricate the work surface of the table and the dough itself with linseed oil so that it does not stick to your hands. Roll out the dough into a round layer 2-3mm thick. Cut it into triangles. Place a slice of banana in each triangle and roll the dough into a roll.
Place all bagels on a baking sheet lined with parchment paper and greased with butter. Brush the bagels with yolk. Place the baked goods in an oven preheated to 180°C for 20 minutes.
Before serving, decorate the bagels with powdered sugar or melted marmalade. Serve with hot drinks: tea, coffee, cocoa.