Lunch
That way they are well-rested and not over hungry, and if they react you have enough time before evening that it won't cause problems overnight.
There is no rush to start with solids - here it's reccomended that you don't start until 6mo. Some babies aren't interested until 8mo, but that is fine as long as they are drinking plenty of milk (formula or BF).
We started a week before he turned 6mo with veggies and fruit - he was interested by then but wasn't before!