I checked TCB and the sidebar says the cake should be 1.5” at the sides and 1.75” in the middle, so it does sound like your cake was the right height. Many of Rose’s cakes are slightly domed coming out of the oven and then cool to a flat shape, but this one is intended to have a slight dome even when cool.
Since your cake was flat and the right height, it almost sounds like your sides were too high, rather than having a problem with the center. How did you test for doneness, what sort of cake strips did you use, and how long did the cake bake?
I baked a different almond cake - gateau breton from RHC- and my oven was running cool, so the cake took longer than the time specified to be done. The result? Very dry from being in the oven too long, even though it had reached the correct internal temp. I tried it again with a hotter oven and it was perfect- moist, tender, great. I’m wondering if this could be the problem with your cake- in the oven too long, so the top dried out and the cake baked flat. Despite being dry, the solution is a hotter oven. (or thinner/less soaked cake strips, if that is what was slowing down baking).
Hope something there helps. I’ll be out of town for the next few days, hopefully someone else can jump in if this doesn’t solve your problem (or you could ask Woody over on the blog).