In a large bowl, combine the rice, 1 1/2 cups of the milk, the sugar, vanilla, lemon zest, and salt. In a small bowl, beat the remaining 1 cup milk and the eggs until thoroughly blended; stir into the rice mixture. Pour into a 2 or 3 quart casserole. Bake in a preheated 350F oven for 30 minutes. Stir gently and dust with the nutmeg. Continue to bake 40 more minutes, or until set and lightly browned. Cool slightly, then serve warm, with cream, if desired.