1. In a small bowl, mix together espresso and liquor.
2. In a heat proof bowl over a double boiler whisk together 6 yolks, sugar, and orange zest, until the mixture is thick and pale blonde in color.
3. Remove and allow this to cool.
4. Add in the mascarpone cheese and sugar, in yolk mixture and fold well until the mixture turns pale yellow in color.
5. In another bowl, beat the egg whites and cream of tartar until they reach stiff peaks.
6. Lightly fold the beaten egg whites into the mascarpone mixture.
7. Dip the third of ladyfingers in the espresso mixture and place it in the bottom of a serving bowl.
8. Put third of layer of mascarpone cheese mixture over the ladyfingers
9. Dust with lots of Cocoa powder.
10. Repeat last 3 steps to make 2 more layers.
11. Place the bowl in refrigerator until chill or overnight.