In a medium saucepan, combine the milk, 1 cup granulated sugar, 2 tablespoons butter and lemon zest. Bring to a simmer over low heat. Whisk in the semolina and cook, stirring, until the mixture is thick, 6 to 8 minutes. Remove from heat and whisk in the eggs, 1 at a time. Return the saucepan to the heat and cook, stirring constantly, for about 30 to 40 seconds, to cook the eggs. Remove custard from heat and let cool to room temperature.
Preheat oven to 325 degrees F.
In a small saucepan, melt the remaining 2 sticks butter with the oil; use a little to brush an 8-inch round nonstick springform baking pan. In a small bowl, combine the remaining 1/2 cup granulated sugar and 1 tablespoon of the cinnamon.
Stack phyllo on a work surface and cover with parchment paper and then a damp kitchen towel. Working with 1 sheet of phyllo at a time, place 1 of the corners into the center of the pan, and gently press the dough against the inside of the pan so that the dough fits tightly into the pan. Lay a corner of the second sheet of phyllo into the center of the pan, slightly overlapping the phyllo. Press phyllo tightly into the pan. Lay the third sheet of phyllo into the pan in the same manner, covering the remainder of the pan. Now you have 1 layer of dough completed. Using a pastry brush, brush the phyllo with a generous amount of the butter mixture. Lightly sprinkle with cinnamon sugar mixture.
Place 3 more sheets of phyllo into the pan in the same manner, brushing with the butter mixture and sprinkling with cinnamon sugar. Repeat process again with the remaining 3 sheets of phyllo. You will now have completed 3 layers. Fill pan with custard, spreading evenly.
Working with 1 layer at a time, fold phyllo sheets toward the center of the pan. Brush generously with the butter mixture and sprinkle with cinnamon sugar. Repeat folding, buttering, and sprinkling until all layers have been folded toward the center, with the exception of sprinkling the top layer as the sugar may cause it to darken too much. Prick all over with a fork and bake, on a baking sheet lined with a silpat (non-stick French baking mat) or parchment paper, until golden brown, about 1 hour.
Combine the remaining 1 tablespoon of cinnamon with the confectioners' sugar and sprinkle over the surface of the phyllo when removed from oven. Let rest 5 to 10 minutes before slicing. Serve warm or at room temperature.
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