Ask students to tell the person next to them something they learnt in the lecture.

OR

Each student writes down a question related to the tutorial. They pass the question to another student, who has to come up with an answer.

Online synchronous version 

At the end of a webinar session- in the chat pane each student writes a question and tags another student to answer it. Answers are then collected and looked at as a whole group as a summary 

Online asynchronous version 

Using a tool such as a Moodle forum, a collaborative word document, or a shared collaborative board such as Microsoft Planner, each student writes a question and nominates by tagging another student to write up the answer.