The Austrian forward scored a goal and assisted Christian Benteke's winning strike in Villa's crucial victory over their relegation rivals.
Lambert has praised Weimann for making the most of his opportunity in the side.
"I don't think he was a regular in the side but we gave him a chance and he is playing exceptionally well," Clubcall.com quotes Lambert as saying.
"I know his natural position is probably through the middle but that's difficult with the way Christian Benteke and Gabby Agbonlahor are performing. But, whether or not he has to play off the line, he seems to score goals.
"The biggest compliment I can pay him is that he is a brilliant guy who gives you everything and that can take you a long way. It was a brilliant goal that he scored and, for the third goal, he just never gave up the ghost. He's a phenomenal lad to work with."
Weimann has scored 11 goals in 32 appearances for Villa this season.