iOS Rounded corners of grouped - style UITableView

[nacho4d]

I have just created my table view (withStyle:UITableViewStyleGrouped) and populated correctly.

But when draw my custom cell I got it grouped but with an ugly 90 degres corner.

I think I read something about this in some sample or tutorial, but I can't remember well.
I think is was something with a "layout" named method that calculates the size for cells, but I can't remember well.

What I wrote was:

- (UITableViewCell *)tableView:(UITableView *)thisTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *CellIdentifier = @"Cell";
    EVLessonCell *cell = (EVLessonCell *)[thisTableView dequeueReusableCellWithIdentifier:CellIdentifier];
	if(cell == nil)
		cell = [[EVLessonCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier];

... etc ...

return cell;

So, the winner question is .... How can I get my corners rounded?

Thanks in advance.
Ignacio