Recipe calls for Aleppo Peppers, I need the right substitution amounts for cayenne and paprika
Cindy is right, you can just make a bigger batch (particularly if you're planning to use this recipe multiple times) and measure directly out of your pre-mixed batch.  But, if you don't want to do that, you'll want to do some math.

First off, 1 tbsp = 3 tsp, so to simplify your 2 tbsp and 3/4 tsp, you've actually got 6-3/4 tsp of pepper.

Now, you're looking at 4 parts paprika to 1 part cayenne and we can set that equal to  6.75 tsp.

So, that means that you have five "parts".

Now, to find out how much is in each "part", divide 6.75 tsp by 5 parts. Which is 1.35 tsp/part.

We've found out one number! We need one part of cayenne, so we need 1.35 tsp.  This is closest to 1-1/3 tsp but if you want it in something actually measurable (because who has a 1/3 tsp measure, anyway) it's pretty close to 1-3/8 tsp (1.375 tsp).

Now, to get the measurement for paprika you have two options:


multiply 1.35 tsp by 4, which is 5.4 tsp. This, again, doesn't really give us a very useful number but it's pretty close to 5-3/8 tsp (5.375 tsp).
subtract 1-3/8 tsp from the total 6-3/4 tsp (or 6-6/8 tsp) to figure out what's still needed, which is 5-3/8 tsp (in decimals, that's 5.375).


So that's it.


5-3/8 tsp (or 1 tbsp and 2-3/8 tsp) of paprika.
1-3/8 tsp of cayenne.


That all being said, remember this is cooking, it's not a perfect science, so you can fudge things a bit if you like. Your thought to use 2 tbsp and 1 tsp is close.  It's slightly paprika-heavy but it's a lot easier to measure.