Q.variegated dwarf lemon tree
I have a variegated dwarf lemon tree. The fruit is yellow but round. It does not have much juice. What is it? I call it lemon because that’s what the tab says. It smells like a lemon but it is very bitter.

Yes, this is a Lemon Tree variety likely the Eureka Lemon.
The tree will produce a few lemons when it is young and more when it reaches the age of 4 to 5 years.
The fruit will be green with gold stripes when young and matures to a pale yellow.
The Lemons you describe are immature and need more time to ripen.
The tree prefers 8 hours of sun per day and protect it from cold and wind.
All citrus need evenly consistent watering.
Here are some links for you.
https://www.gardeningknowhow.com/edible/fruits/lemons/lemons-stay-green.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-meyer-lemons.htm