In small bowl with mixer at low speed, beat butter, 1.25 c flour, quarter c sugar, 1 egg yolk and half of the lemon peel until dough is well mixed.
Refrigerate, covered, for 1 hour. Preheat oven to 400-degrees. Press one third of dough into bottom of 25 cm springform pan. Bake 8 minutes; allow to cool. Turn oven to 475-degrees. In large bowl with mixer at mediom speed, beat cream cheese just until smooth; slowly beat in 1.75 c sugar until smooth.
With mixer at low speed, beat in 3 T flour and remaining ingredients. except sour cream. At high speed beat 5 minutes.
Press rest of dough around side of springform pan to within 3 cm of top, do not bake now. Pour cheese mixture into pan; bake dozen minutes. Turn oven to 300-degrees; bake 35 minutes. Turn off oven; leave in oven 30 minutes. remove; cool in pan on rack. Chill.
To serve: Remove side of pan. With ladge spatular, loosen cake from plate. Spread top of cheesecake with cour cream to garnish...