1. Melt 1 stick butter in the microwave in a medium mixing bowl. Add the evaporated milk, 3/4 cup of the sugar, and the salt. Stir so that the sugar dissolves. Allow to cool.
2. Dissolve the yeast in 1/4 cup lukewarm water and stir in another teaspoon sugar. Allow to stand for 10 minutes, until foamy. If the yeast does not foam up, it is no good, so you'll have to start over with new yeast and sugar.
3. Add the yeast mixture to the butter and milk mixture. Add the eggs and lemon zest and whisk together vigorously, until well blended.
4. Whisk in the flour, 1 cup at a time, until you have a thick paste - about 3 cups flour. Then switch to a wooden spoon and continue adding flour and mixing well. Do not add more than 6 cups flour, or your cake will be too dense. When you have added all the flour, turn the dough out onto a lightly floured wooden board and knead it with your hands, which you have dusted with flour, until the dough is smooth and elastic, about a dozen turns.
5. Place the dough into a large clean bowl that you have sprayed with vegetable oil cooking spray. Turn the dough to coat all sides with spray. Cover the bowl with a tea towel and allow the dough to rise in a warm place until doubled, about 1 hour.
6. Make the cinnamon-sugar filling: Combine 1/2 cup sugar and cinnamon in a small dish and stir well.
7. Punch the dough down and divide the dough in two. Roll out each half into a 10 by 15-inch rectangle. Brush each rectangle with half of the melted butter (1/2 stick total) and then sprinkle each rectangle with half of the cinnamon-sugar filling mixture. Roll up along the long end like a jelly roll. Press the roll together at the seam, sealing with water if necessary. Wind the two rolls together, forming one thick piece. On a baking sheet sprayed with vegetable oil cooking spray, form the dough into a circle and seal the ends together.
8. Cover with a tea towel and allow the cake to rise in a warm place for about 1 hour (when it rises, the center will close up and it will look like a bumpy "cake"), until it almost doubles in size.
9. Preheat the oven to 350°F. Whisk the egg white with 1 tablespoon water. Brush the top of the cake with the egg white. Bake the cake for 35 minutes, until it is browned and sounds hollow when tapped.
10. Make the white icing: Combine confectioners' sugar and milk in a small dish and whisk until smooth. If the mixture seems too thin, add a little more sugar. If it won't drizzle, and a little more milk, 1/2 teaspoon at a time.
11. Make the colored sugar: Place 1/4 cup sugar in each of three custard cups. Put 1 drop of yellow food coloring into one, then, using your fingers, grind the color into the sugar until all of the granules are colored. Do the same using green food coloring, and in the third cup, blend 1 drop of red coloring and 1 drop of blue coloring to make purple.
12. Allow the cake to cool for a few minutes on a wire rack. Drizzle with icing and sprinkle the colored sugar in random patterns over the white icing. Slice across the width of the cake into think slices to serve.