• Preheat oven to 350 F. Rinse, dry, and finely zest the peel of one orange; set zest aside for batter. Slice orange horizontally in 1/6 - 1/4 inch thick rings. Look over the slices for any wayward seeds, picking  them out with a paring knife as needed. (If orange slices don’t fit in pan as whole circles, feel free to cut edges as needed. If one orange is not enough to cover the bottom of the pan with slices, you may need to repeat the zesting and slicing process with a second orange, but please only use the amount of zest in the batter from the first one.)
• In a 10 inch ovenproof skillet, melt 1/4 cup butter with 1/2 cup brown sugar, whisking over low/medium heat. When butter has melted and sugar starts looking less grainy, let bubble while whisking for another 30 seconds or so. Remove from heat, whisk in 2 teaspoons soy sauce, and stir until even. Gently lay the orange slices in one layer on the butter mixture, prettiest sides down. Set pan aside.
• In a separate container, melt the remaining 1/3 cup butter; set aside. In a large bowl, beat the remaining 1.25 cup brown sugar with the eggs. Beat in the melted butter until smooth, gradually adding both vanillas. Sift the flour, baking soda and powder over the egg mixture. Begin to mix (batter will seem dry), gradually adding the milk, water and 3 tablespoons soy sauce as you go. Scrape bowl often with spatula as you mix well. Fold in orange zest until evenly dispersed. Gently pour batter onto the orange slices in skillet.
• Place pan in center of oven and bake for about 35 minutes, until center no longer jiggles when shaken and a wooden skewer or toothpick inserted in the middle comes out batter-free; a few moist crumbs are fine. (Begin checking at the 25 minute mark, since every skillet is different.) Carefully remove cake from oven (handle will be hot). Let cool in pan for 30 minutes to an hour, until pan is still quite warm but cool enough to handle. Loosen sides of cake with a butter knife and gently invert cake onto a large plate. Serve warm, cutting into pieces with a sharp knife straight through the orange slices.
• For premium texture, this cake is best eaten soon after baking; but if you must wait longer than noted above, leave it in the skillet until ready to serve (up to overnight). After it’s completely cooled, cover loosely with foil. When ready to serve, remove foil, place skillet over low-medium heat for about a minute to help loosen the oranges, then loosen sides with a butter knife and invert. For gooey deliciousness, warm the slices and serve with vanilla ice cream.

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