Add Row Number Dynamically To Query Results In T-SQL

Aloha fellow developers!

I have this scenario wherein I need to display row numbers in my result set given that the rows don't have a ID column and each row number represents the month number of a specific month.

SELECT 
 A.fsyear_num as 'Fiscal Year',
 [MonthName]
FROM CTE_GrossProfit_SalesByClass_Current_FSYear A

I know that row number is the solution but I need to tweak this to handle my requirement. After reading the forums and docs, I found out that adding a select statement with COUNT() inside the Over By clause is the solution.

SELECT 
 A.fsyear_num as 'Fiscal Year',
 ROW_NUMBER() Over(Order BY (Select Count(*))) AS MonthNum,
 [MonthName]
FROM CTE_GrossProfit_SalesByClass_Current_FSYear A
ORDER BY MonthNum ASC