How to publish Tombstone Avro value using JAVA ProducerRecord?

I have avro schema created.

If I call

ProducerRecord pR=new ProducerRecord<>(key,topic,null);

I get error:

I figured out the method to handle delete connector which should have tombstone messages.
Set “optional”:true to all properties in avro schema and use Drop$Value to create tombstone message.
Java Service (String,Avro) → Kafka → Connector (delete.enabled=true, Drop$Value) ->SQLServer