Snack sandwiches with herring on black bread

How to make sandwiches? Moreover, so as not to mess with them for a long time and they were tasty and nutritious. In fact, it's very, very simple. I clean the herring, gut it and remove the fillet from it. I grind butter in a wooden mortar with tomato paste. It turns out an interesting tomato oil, which in itself can serve as the basis for a variety of festive and everyday sandwiches. I boil the eggs hard-boiled and when they cool down under a stream of cold water, I cut them into medium-thick rings. Finely chop the onion, and cut the herring fillet into pieces about the size of a third of a bread slice. When everything is ready, I immediately proceed to the most important thing - creating the most beautiful sandwiches. I smear tomato butter on bread. In the middle I put the egg ring in such a way that the yolk is visible from above. On the left I sprinkle with chopped onion very finely, and on the right I put a piece of herring fillet. I put the sandwiches on a large platter and keep them in the refrigerator for twenty minutes before serving. I usually serve them at the very beginning of the festive dinner before the main dishes, so that the guests can thoroughly warm up their appetite and be ready to enjoy a rich and hearty meal: lots of meat delicacies and vegetable salads. A walnut cake is expected for dessert, but it's still a long way off: everyone is enjoying these wonderful sandwiches. For the first time I tried these cold sandwiches at a friend's party and I liked them so much that after lunch I asked for a recipe.