You'd have to do something to make the Germans
emphasize the Western allies more in their war planning. A cease-fire after Kursk, maybe. This is full of holes but here goes:
After their precious Tigers and Panthers fail to do the job (albeit, barely), Hilter and/or OKW have a bizarre attack of rationality and recognize that
1941=country-wide offensive
1942=theater offensive
1943=can't lop off one measly salient
Alternately, you could have the Germans discover their communications have been compromised by LUCY and decide to play for time. Either way, they offer a cease-fire with some boundary line sweeteners.
Immediately after Kursk, the Soviets are in no shape to do anything offensive and Stalin figures, free territory, why not. It's not like the cease-fire will last one second beyond when he wants it to, anyway.
Fast forward a couple months and the Red Army is ready, as they were in OTL, to blow a huge hole in Army Group Center. STAVKA is pushing loudly for this, so loudly that Stalin begins to think his generals are getting out of hand. With the military situation stabilized, he turns to the political situation, asserting his authority to maintain the cease-fire and do any other manner of silly thing by whatever means necessary. No fall or winter offensive in 1943, a spring 1944 offensive is possible.
As the cease-fire holds, the Germans begin to slowly and very cautiously shift air and even a few ground assets west (while actually making modest defensive preparations in the east). As the ground thaws, the Red Army is ready and Stalin is finally willing but now Soviet spies in the West are reporting an invasion is scheduled for June. As this information becomes more solid, and with the political lessons of 1943 in mind, it is decided to wait.
D-day still achieves tactical surprise but now there are two extra divisions -- one with Panthers -- available plus a whole lot more fighters. The German screw-ups are unchanged and the beachhead is established but the Allies suffer heavier casualties from the heavier dislodge effort when it is eventually launched.
June 8: STAVKA confirms a major amphibious assault. June 9: the Red Army rolls. Versus OTL, the Soviets have farther to go and the Germans have suffered fewer losses. But the Soviets are also much better prepared.
In the West, the Allies are unchanged and the Germans are stronger. The different balance of forces opens up the possibility of actually defeating the US and Britain, an option not available in the East. So the Luftwaffe gives up on the air war over Russia in order to try to provide cover for the panzers. Even with air dominance from the outset, the few top-of-the-line tanks the Allies faced in OTL gave them fits. Now there are more tanks and less ability to get at them through the air.
Payoff
The German attempt to drive the Allies into the sea fails but the liberation of France is slower and more costly. Meanwhile, the Soviets are able to make up for lost time with the Germans focusing their attention on the West. Instead of logistical exhaustion in front of Berlin in April 1945, the Soviets arrive in June in pretty good shape. The Allies are barely slugging into Germany. The battle of Berlin is horribly costly, then the Allies insist on a partion where they get part of Berlin and a larger chunk of Germany. Stalin says nothing, merely occupies most of the country. The Allies declare their nuclear capability. Stalin decides he needs more bargaining chips, like more German territory.