Heat the oven to 325 degrees. In the food processor or electric mixer, mix the butter with the sugar and then add the eggs one by one. Add the salt, vanilla, lemon juice and flour little by little.
Grease a 9x9x2 mold. Pour half of the mixture into the bottom of the mold and arrange until the bottom is covered. Then cut the pasta into strips and place over the flour mixture. Then cover the guava paste with the rest of the flour mixture and arrange until smooth.
Bake for 40 to 45 minutes. Let cool, dice and decorate with confection sugar.