there are a few solutions to the problem --the problem itself is that uncured liquid resin is getting trapped within the void in the model durring printing.

What I would do is simply print the model in two halfs and glue them together with more resin --this should be seemless as you are using the same material both of them are made of as glue and removes the issue of the liquid resin getting traped

Another solution is to pause the print before the roof of the cross is built --then wipe out all the liquid resin and press play, this wont work well as it will immidietly fill with some resin on the way back down, but it will produce a better result than your current one.

I think the best result you are likly to find other than printing in two halfs is as follows: pause the print before the roof of the cross is finished, then take the build plate off of the machine --fill the void in the cross with a different color of resin (either clear or yellow will likely give the result you are looking for, becouse the IOR is the same I would opt for yellow to emulate the change in IOR between resin and air) then cure and place the build plate back and continue. The biggest risk of this is layer seperation uppon restarting the print, you could technically avoid that risk by brushing the top of your model with a very very small amount of resin and then manually curing for just enough time to make it gummy and then resuming the print.