Is it possible to reindex specific blocks? I came across a block on my Fullnode that throws an error when attempting the gettrawrtransaction RPC. 

No such mempool or blockchain transaction. Use gettransaction for wallet transactions.

It's only one block so far that seems like it got corrupted or improperly indexed. If I change the block/transaction, the JSON-RPC call works. I have txindex=1 set in bitcoin.conf 

My question is, can I tell bitcoind to reindex only that particular block 282455, or do I need to reindex the entire blockchain? If so, what's the fastest method? Setting a higher dbcache?
No, to the best of my knowledge there is no user-level command to reindex specific blocks.  It's all or nothing.

If you want such a feature you'll have to write the code.

It seems to me kind of unlikely that the index would be wrong only for one specific block, so I would suggest looking for other explanations for the behavior you're seeing.