Apples and oranges.
There are no majority-Jewish CDs. The most heavily Jewish Congressional Districts are something like less than 40% Jewish. Only 20 or so CDs have as many as 10% Jews.
By contrast, there are at least 25 majority-black CDs, with dozens more at 25% or more.
As of data from January of 2014, the top three Congressional Districts with the most Jews are:
New York 10th, 37.62%
Florida 21st, 24.27%
New York 3rd, 22.01%
I used to work in Florida’s 15th, which is now mostly covered by the 21st. I was told that, of likely voters, over 80% were Jewish. They might not hold the majority, but they turn out in HUGE numbers.