To find the unit rate of muffins per cup of almonds, you divide the total number of muffins by the total number of cups of almonds.
Manny makes 36 muffins and uses 4 cups of almonds:
\[ \text{Unit rate} = \frac{\text{Total muffins}}{\text{Total cups of almonds}} = \frac{36 \text{ muffins}}{4 \text{ cups}} = 9 \text{ muffins per cup} \]
Therefore, the correct answer is:
9 muffins