We began a tradition where the first thing you said when you sat down to eat was a compliment or something positive about the meal.
“Yum mom! This looks great!”
“Wow! You made rolls! Thanks!”
“This smells so good! I could smell it all the way downstairs!”
“This is such a fancy meal, it must have taken you a long time to make. Thank you!”
A few times, when saying something negative things about the meals became a habit for our kids, we started giving them a small reward if the first thing they said when they sat down was a compliment. So if they sat down and said "Wow! This looks great!" then I'd hand them a small treat (like 1 fruit snack or M&M). When we first begin a technique like this the compliments (or good behavior) IS not sincere. But as time passes the good behavior becomes more of a habit. Soon, as it has become part of your daily routine and expectations, you can wean them off the rewards.