Just moved in and there is no kitchen light. There is a ground, two whites nutted together and two blacks AND a white nutted together. My new fixture has a standard hot and neutral. How do I connect?
A lamp connects to switched-hot and neutral.
The two blacks and a white nutted together are always-hot. This is not of interest to you, unless you want the lamp on 24x7. Leave it alone.
For your information, there is an obsolete wiring technique called a "switch loop". This is where power comes into the lamp, and the switch is a spur branch. It carried 2 wires to the switch: always-hot went to the switch, and switched-hot came back. It goes without saying these two wires are in the same cable.
Since only 2 wires were used, they used common /2 cable, in which the colors are black and white. White is usually neutral, but not here. To reduce confusion, the rule is that the always-hot must be white, to make it more obvious to people with voltage testers that this isn't neutral. The black, then, is switched-hot.
The white in the black bundle goes to a cable. The black in that cable, which you have not mentioned yet, is the switched-hot. That connects to the lamp's black wire.
The group of all-white wires are actual neutral. Those wires are doing important tasks. However, your lamp needs neutral, so its white needs to be added to that bundle.