If an investment owned by an estate is split between beneficiaries, how do you pay the tax on the change in value between the date of death and the distribution date?

This would be for investment funds/accounts that were not sold so there's no 1099-B, but each of two beneficiaries received have off the shares.

Retirement tax questions

you won't pay any tax until you sell those assets

the estate must pay its own taxes due, if any,  before distributions can be made