To make the pastry: in a food processor combine 3 cups of flour, sugar and salt until on/off turns. Add fennel and process for 30 seconds. Blend in 1 cup of butter (broken into pieces) using on/off turns until mixture resembles coarse meal. Add eggs while machine is running and mix just until dough comes together. You may need to add a bit more flour if dough doesn't come together. Remove dough from processor and shape into disc and wrap in wax paper and refrigerate for several hours or overnight.
To prepare filling: melt the 3 T of butter and oil in a large skillet over medium heat. Add leeks and shallots and cook until soft (10 minutes). Add garlic and saffron and stir 2 minutes more. Blend in liqueur and cook for 2 more minutes or until it evaporates. Stir in parsley and salt and pepper. Cool to room temperature before proceeding.
To assemble tart: preheat oven to 425 degrees F.
On a floured board roll dough out to fit 11-inch tart pan circle (about 1/4 inch thick). Fit into pan with a removeable bottom, and trim edges. Chill 30 minutes.
Line pastry with foil and fill with dried beans or pie weights. Bake for 8-10 minutes, remove foil and weights and bake for 10 more minutes or until golden.
Spoon in leek mixture. Sprinkle with cheese. Top with tomato slices, overlapping circles.
Whisk together eggs, cream and salt and then pour over filling.
Set tart on a baking sheet and bake for 30-40 minutes or until filling is set. Brush with melted butter during last 5 minutes of baking. Cool in pan on rack.