For the tuna tortellini, knead the ingredients for the dough until smooth, shape into a ball and wrap in plastic wrap.
Let the dough rest in the refrigerator for a few hours. For the filling, chop the shallots and chives. Grate the zest of the lemon, drain and chop the tuna.
Mix the ingredients with crème fraiche. Roll out the pasta dough into sheets, place the filling on a pasta sheet with teaspoons at the appropriate distance (depends on the size of the pasta pockets).
Slightly moisten the dough around the filling so that the second dough sheet bonds well. Place the second pastry sheet on top of the mounds of filling and press down well.
Cut out tortellini (with a pastry cutter, pastry wheel or drinking glass). Repeat this process until dough and filling are used up.
Let the finished tortellini dry briefly on a floured surface, bring sufficiently salted water to a boil in a saucepan and let the tortellini simmer for about 8-10 minutes.
Melt the butter in a pan, add olive oil and salt. Slice the lemon and brown it in the butter with the sage leaves.
Slide the cooked tortellini into the butter and serve immediately.