Heat the oven to 350ºF and set a rack in the middle slot. Spray an 11-inch tart pan lightly with cooking spray and line a rimmed baking sheet with aluminum foil.

Combine the flour, butter, sugar and salt in the bowl of a food processor. Pulse until crumbly, about 15 one-second pulses. (You can also add everything to a bowl and cut the butter into the flour mixture with a pastry cutter or fork). Add the water and continue to pulse until the dough sticks together when pinched between your fingers.

Tip the dough into the pan and use fingers to press it evenly on the bottom and up the sides. Use a fork to prick the bottom of the dough a few times. Place in the freezer to chill for at least 15 minutes (or wrap in plastic wrap and refrigerate overnight). Place it on the prepared baking sheet. Place another piece of foil over the chilled crust and fill it with pie weights, dry beans or even better, sugar. Bake until crust is light golden brown and baked through, 35-45 minutes. Let cool and remove the sugar (and the foil on top of the crust).

Heat the oil in a large skillet set over medium-high heat. When the oil is shimmering, add the leeks and lightly season with salt and pepper. Cook, stirring frequently, until the leeks are soft and translucent, about 5 to 7 minutes. Add the chopped ramps and cook until wilted, about 2 to 3 minutes longer. Transfer to a bowl and set aside.

In a medium bowl, stir together the goat cheese, cream, lemon zest, thyme and eggs. Season with salt and pepper and stir until mostly smooth. A few small lumps of cheese is fine.

With the tart pan still on the rimmed baking sheet, spread the leek and ramp mixture over the bottom of the crust. Pour the custard mixture over the leeks. Arrange the whole ramps over the custard. Bake until the center is just firm to the touch and the tart is lightly golden, 25 to 30 minutes.

Transfer the tart to a wire rack and let it cool for at least 15 minutes. Un-mold the tart and transfer to a serving platter. Serve warm or at room temperature.