Lemon-Poppyseed Upside Down Cake

1 pkg. Lemon-Poppyseed Bread Mix
1 egg
8 ounces light sour cream
1/2 cup water
Sauce:

1 tablespoon butter
3/4 cup water
1/2 cup sugar
juice from one lemon (about 1/4 cup)

Mix the first 4 ingredients together until well moistened.
Spread batter in a lightly greased 3 1/2 quart crockpot.
Combine sauce ingredients in a small saucepan; bring to a boil. Pour boiling mixture over the batter; cover and cook on high for 2 to 2 1/2 hours. Edges will be slightly browned.
Turn heat off and leave in the pot for about 30 minutes with cover slightly ajar.
When cool enough to handle, hold a large plate over the top of the pot then invert.