Position a rack in the lower third of the oven and preheat to 375 degrees. Fit the pie crust in a 9-inch pie pan; crimp the edges. In a large bowl, whisk together the sugar, eggs, butter, lemon juice, 2 tbsp. cream, the cornmeal, cornstarch and salt until well combined. Pour the filling into the prepared crust.
Transfer the pie to a baking sheet and bake until the filling is mostly set and the center is slightly jiggly, about 40 minutes. If needed to prevent overbrowning, cover the crust loosely with foil halfway through baking. Let the pie cool completely.
Beat the remaining cream until soft peaks form. Gently fold in 1/2 cup of the toasted coconut. Top the pie with the whipped cream and sprinkle with the remaining 1/4 cup coconut.