Leaving lasagna (or any perishable food) out at room temperature for 8 hours is not recommended, as it falls into the "danger zone" where bacteria can multiply rapidly. The danger zone refers to temperatures between 40°F (4°C) and 140°F (60°C), which is the range where bacteria can grow and cause foodborne illnesses.
Even if the lasagna was covered during the time it was left out, it may still have been in the danger zone for an extended period, and there is a significant risk of bacterial contamination. Covering the food may slow down the rate of bacterial growth slightly, but it won't prevent it entirely.
Putting the lasagna in the fridge after the 8 hours doesn't guarantee safety either, as refrigeration won't completely eliminate the bacteria that may have started to grow during the time it was left out.
To ensure food safety, it's best to follow the "2-hour rule": perishable foods should not be left out at room temperature for more than 2 hours. If the ambient temperature is above 90°F (32°C), the time limit reduces to just 1 hour. After that, the food should be discarded to avoid the risk of foodborne illness.
In this case, considering the lasagna was left out for 8 hours, it is not safe to eat. Eating food that has been in the danger zone for an extended period can lead to food poisoning and other health issues. It's essential to prioritize food safety and discard any perishable food left out for an extended period to avoid potential health risks.