How to Make It
In a food processor, combine the flour with the sugar and yeast and pulse to mix. Add the butter and 2 tablespoons of the beaten eggs and process just until a dough forms. Scrape the dough out onto a work surface and pat into a flat disk. Wrap in plastic and refrigerate for at least 1 hour.
Preheat the oven to 350°. Let the dough soften slightly, then transfer it to a 10 1/2-inch tart pan with a removable bottom. Press the dough over the bottom and up the side, about 1/2 inch beyond the rim of the pan. Line the dough with foil and fill with pie weights or dried beans. Bake for 10 minutes. Remove the foil and weights, brush the bottom with some of the remaining beaten eggs and bake for 10 minutes longer, or until golden brown.
In a food processor, combine the orange and lemon slices with the sugar, butter and orange liqueur and process to a chunky puree. Add the eggs and process to blend. Pour the filling into the tart shell and bake for about 1 hour, or until just set. Let the tart cool. Cut into wedges and serve warm or at room temperature.