The best way to edit the issues with verb voice and mood in these sentences is:
An hour after Sheila placed the lasagna in the oven, we smelled a tantalizing aroma and our stomachs began to growl. "You should take it out of the oven, and then you should cut everybody a slice," Cynthia said to Sheila.
This option improves the verb voice by making it active ("we smelled") rather than passive ("was smelled"), and it also clarifies the mood by using "you should take it out" instead of "take it out."