With the fresh beets, to heat the oven to 200°C. To wind every beet in an aluminum sheet with the opaque part to the outside and to cook them up to when they result tender (abour 1 hour). The beets can be cooked the day before. To put the burghul in a tureen and to pour above it 12,5 cls of hot water. To let rest for about 30-35 minutes. To skin the beets a little warmed.To mince half beets and to add them to the burghui, mixing, with the vinegar, 1/2 spoon of sauce of cren, 1/8 of teaspoon of salt and one ground of pepper. To put aside. To cut a slice of 2,5 cms from one of the remained beets and to put it in the blender.To cut the rest of the beets to thin fillets and to maintain in warm. To prepare pasta in the blender, to put 175 flour gs, the egg, the clear, the oil and the puree and to beat for 30 seconds. If the mixture form immediately a ball and it has bathed to the touch, to add other flour, up to let become soft pasta, but not sticky. If instead the mixture doesn't form a ball andresults friable, to add some teaspoon of water. With a machine for the pasta, it is possible to work and to stretchthe puff pastry. To make pastato hand, to put 175 flour gs in a tureen and make the fountain. To add the oil, the egg, the clear, the puree and to gradually mix to the flour. To put pasta on the floured table andto knead for some minute. Pasta is not had to attach to the surface of the table; if it is too sticky, to add some flour, if instead it results hard and crumbled, to add some water to soften it. To continue to knead for aboout 10 minutes, or to knead with the machine. If the machine for pasta is not used, to wind pasta in the transparent film and to let rest it for 15 minutes before stretching it. Make raviolis filling with the stuffing of beet and burghul. For the sauce, to heat the oil in a casserole from the heavy fund, on middle fire. To add the onion and to cook about for 4 minutes, up to when the onion becomes transparent. To lower the flame and to mix the sour whipped cream and the yogurt up to heat them. Attention not to let lift the excitement, the sauce would be separated. To remove from the fire and to add the grass cipollina, the rest of the salt and the sauce of cren. Tender in warm. To put the ravioli in 3 liters water in ebullition with 1 1/2 teaspoon of salt. To taste after 3 minutes. Drain the pasta, to move it in to a course dish and to pour it above the sauce, to garnish the ravioliwith the beet to fillets and to serve immediately.