Preheat oven to 350 degrees Fahrenheit. Line a 10×15-inch sheet pan with parchment paper or grease it well.

Add the lemon juice to a measuring cup or small bowl. Pour the soy milk over it and set aside.

In a mixer fitted with the paddle attachment (if you don’t have one, use the whisk attachment), cream together the margarine and sugar for two to three minutes.

Add the oil and mix until creamy. Add the jam and mix again to combine.

Add the eggs, vanilla extract, baking powder, baking soda, and salt. Mix until smooth.

Stir the soy milk/lemon juice. It should be curdled but still runny. This is your pareve buttermilk.

Alternate adding flour and “buttermilk” to the cake batter, starting and ending with the flour. Mix until just combined; do not overmix.

Add a few drops of food coloring to amp up the color, if using.

Pour the batter into the prepared pan and bake for 40 minutes, until a toothpick inserted in the center comes out clean.