Making UIView transparent

I want to add a UIView to my UIViewController but I want it to be transparent until I decide to create an Oval inside the UIView.

Until I create the oval, I can set my view's alpha to 0 but when I want to add the oval, the background color is still black.

here's what it looks like with a bunch of ovals

In my UIView:

- (void)drawRect:(CGRect)rect
{
    [self pushContext];
    UIBezierPath *oval = [UIBezierPath bezierPathWithOvalInRect:self.bounds];
    [[UIColor redColor] setFill];
    [oval fill];
    self.opaque = NO;
    [self setBackgroundColor:[UIColor clearColor]];

    [oval addClip];
    [self setBackgroundColor:[UIColor clearColor]];

    [self popContext];
}