I would try using a different container. I would use a "light" seed
starter potting soil for the lettuce and just pat them into the soil and not cover them at all. Use a misting bottle to water them so the seeds
don't get washed over the side or to the edge of the container.
With the tomatoes I would be tempted to get different seeds
. They are very hardy and usually will come up no matter what I do to them.
both should show themselves about 10 days after planting if not earlier.
You are starting these indoors right? If you are starting outdoors it may be the temperature that is keeping the seeds
from germinating. Tomatoes like warm temperatures. And although lettuce is a cool weather crop I start it indoors too.