Melt the butter in a large skillet over medium heat. Add the garlic and thyme; saute for 2-3 minutes. Add the spinach; saute until just barely wilted, about 2 minutes. Remove from heat.

In a large bowl, combine the ricotta, egg, salt, nutmeg, and a squeeze of lemon juice. Add the spinach and stir to combine. Transfer some of the mixture to a food processor and pulse a few times to break up some of the spinach pieces (totally optional, but makes for a really nice texture).

Preheat the oven to 375 degrees. Spread a little bit of tomato sauce in the bottom of a 9x13 pan.

Layer with 3 lasagna noodles, 1/3 of the spinach mixture, 1/4 of the tomato sauce, and 1/4 of the cheese. Repeat and pour 1/2 cup water over the two layers.

Repeat once more, ending with noodles, sauce, and cheese. Pour 1/2 cup water over the whole thing again and cover tightly with oiled foil.

Bake for 30-40 minutes; when the liquid is bubbling and the noodles have softened, remove the foil and bake uncovered for 10 more minutes.

Let stand for 10-15 minutes before serving so that the lasagna noodles can soak up all the extra moisture.