There are British growers who now produce tomatoes and salad veg over winter ( Thanet Earth for example ), which means that it is OK to have fresh tomatoes and lettuce in February.
So, now your conscience is clear, this is dead simple.
Get some British grown cherry tomatoes, put them in an oven proof dish with a tablespoon of olive oil and a sprinkling of salt, and put them in a medium heat oven ( or under the grill ).
When the tomatoes have started to burst out of their skins and char a little, take them out, let them cool a bit, add some balsamic vinegar and mix them with the salad leaves.
We had this with the pasta and artichoke hearts.
It was a feast fit for a king. Fortunately, there were no kings around, so we had it ourselves.