Combine the yeast with the warm water and set aside to proof until foamy.
In a mixing bowl (one that fits in a stand mixer, if you have one), combine the yeast with 2 cups flour, 2/3 cup sugar, salt, sour cream, egg replacer, lemon zest, and vanilla extract.
Beat at low speed to combine the ingredients, then mix at medium speed for 5 minutes while adding in 1/2 cup of Earth Balance, one tablespoon at a time.
Beat the batter for five minutes at medium speed until smooth and shiny, and very sticky.
After five minutes, remove the bowl from the mixer and top with the remaining 2 Tbs of flour.
Do not mix it in.
Cover the bowl with a non-terry cloth kitchen towel and set aside to rise for 90 minutes to 2 hours.
After the first rise, mix the the dough to combine the flour on the top.
With the remaining 2 tablespoons of Earth Balance, grease a 9×9 cake pan.
Sprinkle the remaining 1/3 cup sugar in the bottom of the pan.
Halve and pit the plums.
It may be easier to cut around the pits, rather than to pull them out, if your fruit is very ripe.
Slice the pitted plum halves into five or six slices.
I left mine whole because they were very small.
Place cut-side down into the sugar, covering the bottom of the pan.
Pour the dough over the plums and let raise for another 90 minutes, covered with oiled plastic wrap.
Preheat oven to 375º F.
Bake the kuchen for 35 minutes, until evenly golden and slightly cracked.
Remove from oven and let rest for 5 minutes.
Loosen edges with a knife and turn out onto a rack to cool completely before serving.
