Here is a recipe for cake (kasutera, natch) from 19th-century Japanese recipe book Teisa hiroku 鼎左秘録 ("Left-of-the-kettle secret record"):

• One egg
• Sugar, ten monme (about 35 g)
• Flour, ten monme (about 35 g)

Mix the preceding three items well in a bowl, then spread thick paper inside a pot, and pour the mixture in ["どろりと"]. Put the lid on, and on it place an extremely strong flame. Below the pot place an extremely weak flame, so weak that it is barely even there, and bake. To determine whether baked or not, insert a single rice stalk into the pot. If the cake is evenly baked, the stalk will come out clean, with nothing sticking to it; if not, the cake mixture will stick to the stalk.

If you don't have a "cake pot" (kasutera nabe), a square copper pot available in a wide variety of sizes, don't worry: you can use a regular copper pot, and borrow the candle dish from a lantern to use as a lid. You're welcome, and please let me know how it turns out. (If you don't have the candle dish from a lantern, you're out of luck.)

I read this recipe in SUZUKI Shin'ichi and MATSUMOTO Nakako's Kinsei kashi seihō sho shūsei 近世菓子製法書集成 ("Collection of early modern dessert recipe books"), volume II. Suzuki and Matsumoto note that "flame above and below, with the flame above stronger, is well and good, but having the lower flame 'so weak that it is barely even there' is going too far." Quite.