Your cooktop is almost maxing out your circuit, so when that thing kicks on it probably pulls a little more than 20 amps until it settles down. I don't think your dimmers or other switches are the culprit. Have you ever experienced the breaker tripping on this circuit?

 

Hi,

I have a 110v 2400W (full power) cooktop that I plug into a dedicated 20amp plug. When I turn it on and ? use it the kitchen lights flicker as well as some other lights, I narrowed it down to the ones on dimmers.

Are you sure your cooktop is on a dedicated circuit? If so I don't know how it would effect lighting circuits unless something is going on in the panel. How many amps is your main? Are other heavy wattage items running at the same time as your cooktop? You said dimmers plural. Are these separate circuits or two three-way dimmers?
Regardless, I've replaced a lot of dimmers in my life. Those and GFCIs just don't last as long as other switches or outlets. I would replace the dimmers and see what happens. Look for reviews and get high end dimmers.

 

I have a 110v 2400W (full power) cooktop that I plug into a dedicated 20amp plug.

No. That's not a thing. UL will not certify a 2400W appliance on a common 120V plug - not even a NEMA 5-20 plug (20A nominal). Limits on any plug-in appliance is 80% of breaker trip, so 1920W for appliances with a NEMA 5-20 plug (twisted neutral) or 1440W for appliances with a NEMA 5-15 (normal) plug.

So you have done something wackadoodle, like using a UL-listed appliance intended for permanent installation, whose instructions call for a 25-30A circuit and don't authorize cord-and-plug connection... or you have something not UL-listed at all e.g. bought mail-order from you-know-where. Solve whatever that problem is and good chance the problem will clear up.

The symptoms you describe might be caused by arcing in the wiring on this circuit, due to backstabs or improperly torqued terminals. Obviously arcing generates a lot of spikes.

 

Seharper has a point... Iam. Curious is your plug coming from your stove a factory wired plug? If so can you look on the back of the stove and give us the Nameplate information? Once we determine your stove isn't drawing more continuous power than it should.. we can narrow down the problem.
Iam not used to seeing plug (NEMA 5's) in cook tops..usually they are hardwired..if iam thinking of the right type..
As said above flickering of circuit is usually caused by transit's/arcing which usually cause from a loose connection..I have also seen lighting circuits from low grade drivers in LED lighting cause flickering...
When checking the info on the cook top be sure to look for UL listing as well...

 

What year was the home built or most recent permitted kitchen remodel?

 

Is this an induction cooktop? I could not even imagine trying to cook anything much more than a fried egg on a 2400 way stove top (assuming it has more than one burner). If it’s induction they work by magnetism and the magnetic fields may be interfering with your LEDs and dimmers

 

@wwwdiyc
How about make and model number. That helps us